Kinetic study on biphasic recognition chiral extraction for separation of α‐cyclohexyl‐mandelic acid enantiomers

BACKGROUND: Chiral solvent extraction is a potentially attractive chiral separation technique. It is essential to know the intrinsic complexation kinetics for selection, design and operation of reactive extraction equipment and for reliable scale‐up. The objective of this research is to study the kinetics of biphasic recognition chiral extraction of α‐cyclohexyl‐mandelic acid (α‐CHMA) enantiomers using a modified Lewis cell. RESULTS: The experimental results demonstrate that the extraction reaction kinetics is fast, and the reactions are first order with respect to α‐CHMA and second order with respect to D‐IBTA, with forward rate constants of 6.54 × 10^?4 mol^?2 m⁶ s^?1 for S‐α‐CHMA and 6.84 × 10^?4 mol^?2 m⁶ s^?1 for R‐α‐CHMA. With increase of HP‐β‐CD concentration in aqueous phase, enantioselectivity increases, while the overall mass transfer coefficients decrease. CONCLUSIONS: Sufficient enantioselectivity and fast kinetics of extraction can be obtained in the BRCE system at HP‐β‐CD concentration of 0.1 mol L^?1 and D‐IBTA concentration of 0.2 mol L^?1. These data will be useful in the design of extraction processes. Copyright © 2012 Society of Chemical Industry     

Enantioseparation of chiral aromatic acids in process intensified liquid–liquid extraction columns

Enantioselective liquid–liquid extraction (ELLE) is a powerful alternative to common technologies for separation of racemic mixtures. The first application of ELLE for aromatic acids in liquid–liquid extraction columns is described. The ELLE is investigated experimentally and theoretically for phenylsuccinic acid (PSA) as a representative for aromatic acids. A racemic mixture of (R/S)‐PSA is separated with hydroxypropyl‐β‐cyclodextrin as selector molecule. The ELLE obtained the highest operative selectivity (α_op = 1.8–2) for low pH‐values and temperatures. Because of the low operative selectivity, a countercurrent process is necessary to separate both enantiomers completely. The countercurrent process is investigated in process intensified extraction columns (Ø_in = 15 mm) with a high number of equilibrium stages. The experiments demonstrate a good symmetric separation with an enantiomeric excess of 60% and yields of 80% for both enantiomers. Finally, the back extraction is investigated to recycle the selector molecule and increase the efficiency. © 2014 American Institute of Chemical Engineers AIChE J, 61: 266–276, 2015     

Reactive solvent extraction of amino acids with cationic extractants

A mixture of amino acids (arginine, phenylalanine, alanine, glycine and aspartic acid) in solution was extracted by four acidic extractants (dinonylnaphthalenesulphonic acid (DNNSA), di(2-ethylhexyl)monothiophosphoric acid (D2EHPA(S)), di(2-ethylhexyl)phosphoric acid (D2EHPA) and Versatic 10) in toluene. The extractive capacity of the organic phase for the amino acids, using DNNSA, D2EHPA(S) and D2EHPA was found to decrease in the order arginine>phenylalanine>alanine>glycine>aspartic acid, although at low pH values phenylalanine>arginine occurred for D2EHPA(S) and D2EHPA. Separation factors derived for pairs of amino acids were in the range 2·0 (glycine–aspartic acid) to 20·1 (alanine–glycine). The extractive and loading capability of the extractants for the amino acids was found to decrease in the order DNNSA>D2EHPA(S)>D2EHPA>Versatic 10, which follows the reverse order of their respective acid dissociation constants. DNNSA was shown to be a promising extractant for the extraction and fractionation of amino acids. © 1998 SCI     

Extraction equilibria and separation of phenylalanine and aspartic acid from water with di(2‐ethylhexyl)phosphoric acid

The distribution equilibria of single and binary L ‐phenylalanine and L ‐aspartic acid between water and a kerosene solution of di(2‐ethylhexyl)phosphoric acid (D2EHPA) were studied. It was shown that the distribution ratios of phenylalanine generally increased with increasing aqueous pH (2–5) in the D2EHPA concentration range 0.1–0.5 mol dm^?3, but those of aspartic acid decreased with increasing solution pH. Different reaction stoichiometries were proposed for the extraction of phenylalanine and aspartic acid under the conditions studied. The extraction equilibrium constants were obtained. Competitive extraction in binary systems was more apparent in the pH range where the cationic form of amino acids was not predominant. The present results indicated that selective separation of phenylalanine to aspartic acid was possible with this cationic extractant when they were extracted at higher pH and stripped using higher acidity of HCl solution. Copyright © 2006 Society of Chemical Industry     

冠醚化学交换分离锂同位素的影响因素分析及进展

锂同位素6 Li和7 Li是核聚变所需的重要原料,故锂同位素分离是核能开发必须解决的关键技术。本文系统综述了以冠醚类化合物为化学交换体系分离锂同位素的研究进展,详细讨论了冠醚分子的结构如冠醚环大小、给体原子种类、侧链种类,以及锂盐配位阴离子种类,溶剂种类,化学交换温度等因素对冠醚锂同位素分离效应的影响规律。结果表明,冠醚类化合物具有高的锂同位素分离因子,是非常有前途的锂同位素分离方法,但是以小分子冠醚为萃取剂的液-液萃取体系冠醚易于流失,无法重复利用,因此其未来发展方向是制备冠醚固载聚合物,采用固载冠醚的液-固体系分离锂同位素,提高分离效率,以实现其工业化应用。     

Modelling and experimental evaluation of reaction kinetics in reactive extraction for chiral separation of amines, amino acids and amino-alcohols

This paper reports on determination of the intrinsic reaction kinetics in reactive extraction of chiral compounds. It is important to know the mass transfer rates and reaction kinetics separately for a reliable scale-up. A kinetic model is developed to interpret the experimental data from the selected model reactor, the modified Lewis cell. The two-phase homogeneous reaction model was selected over the interfacial reaction model, because physical partitioning is considerable in all systems studied. It was shown by simulations and by theoretical considerations that conventional regime analysis fails for reactive extraction in a number of regimes, because the conditions of an irreversible reaction and a negligible resistance to mass transfer in the non-reactive phase are generally not fulfilled in reactive extraction. Furthermore, it follows from the simulations that enhancement of mass transfer by reaction may be partly invisible. Finally, it becomes clear that only the fraction of the species that is in the right ‘extractable’ form should be used in the calculations. As the conventional regime analysis cannot be applied to determine the reaction kinetics in the chiral systems, first the mass transfer rate was measured during physical extraction to determine the location of the main resistance to mass transfer. Then the enhancement of mass transfer was measured during reactive extraction. By model simulation, it was determined how much enhancement of mass transfer should be observable. In this way, it was concluded that the reaction kinetics of the azophenolic crown ether system are between fast and instantaneous, and the reaction kinetics of the Cu(II)-N-dodecyl-L-hydroxyproline system are between slow and fast. The Lewis cell is not the most suitable model contactor to determine reaction kinetics in reactive extraction systems.     

Advanced Monte Carlo simulations of the adsorption of chiral alcohols in a homochiral metal‐organic framework

Grand canonical Monte Carlo (GCMC) simulations with configurational biasing were used to study the enantioselective adsorption of four alkanols in a homochiral metal‐organic framework, known as hybrid organic‐inorganic zeolite analogue HOIZA‐1. Conventional GCMC simulations are not able to converge satisfactorily for this system due to the tight fit of the chiral alcohols in the narrow pores. However, parallel tempering and parallel mole‐fraction GCMC simulations overcome this problem. The simulations show that the enantioselective adsorption of the different (R,S)‐alkanols is due to the specific geometry of the chiral molecules relative to the pore size and shape. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2324–2334, 2014     

Enantioseparation via EIC‐OSN: Process design and improvement of enantiomers resolvability and separation performance

This article presents a mathematical model to assess and optimize the separation performance of an enantioselective inclusion complexation‐organic solvent nanofiltration process. Enantiomer solubilities, feed concentrations, solvent compositions, permeate solvent volumes, and numbers of nanofiltrations were identified as key factors for process efficiency. The model was first tested by comparing calculated and experimental results for a nonoptimized process, and then, calculations were carried out to select the best operating conditions. An important finding was that the optimal configuration varied with the objective function selected, e.g., resolvability versus yield, with a boundary on product optical purity. The model also suggested that the process efficiency could benefit from diafiltration of the distomer and from the use of higher feed concentrations. However, the latter strategy would result in higher losses of eutomer. To address this drawback, a multistage process was evaluated using the verified process model. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

油酚分离过程低共熔溶剂的筛选及萃取性能研究

低温煤焦油中酚类化合物的高效分离在工业上具有重要意义。采用COSMO-RS模型对40种用于间甲酚-异丙苯分离的低共熔溶剂进行筛选,结合σ-profile和σ-potential对筛选得到的低共熔溶剂的高萃取性能进行分析。并采用液液相平衡实验对筛选结果进行验证,优化了萃取工艺条件。结果表明,COSMO-RS模型筛选得到的氯化胆碱(ChCl)∶乙二醇(EG)(1∶2)、ChCl∶丙三醇(Gly)(1∶2)、ChCl∶乳酸(LA)(1∶2)三种低共熔溶剂与间甲酚之间存在较强的氢键相互作用,与异丙苯之间存在排斥作用。液液相平衡实验证实了COSMO-RS筛选结果的可靠性,其中ChCl∶EG(1∶2)具有最高的分配系数和选择性系数,且黏度最低,被选定为最佳的低共熔溶剂。在25℃、ChCl∶EG(1∶2)与模型油质量比为1∶1时,ChCl∶EG(1∶2)对间甲酚萃取率高达98.41%,同时异丙苯夹带量仅为8.41%,并且具有良好的循环使用性能。     

油酚分离过程低共熔溶剂的筛选及萃取性能研究

低温煤焦油中酚类化合物的高效分离在工业上具有重要意义。采用COSMO-RS模型对40种用于间甲酚-异丙苯分离的低共熔溶剂进行筛选,结合σ-profile和σ-potential对筛选得到的低共熔溶剂的高萃取性能进行分析。并采用液液相平衡实验对筛选结果进行验证,优化了萃取工艺条件。结果表明,COSMO-RS模型筛选得到的氯化胆碱(ChCl)∶乙二醇(EG)(1∶2)、ChCl∶丙三醇(Gly)(1∶2)、ChCl∶乳酸(LA)(1∶2)三种低共熔溶剂与间甲酚之间存在较强的氢键相互作用,与异丙苯之间存在排斥作用。液液相平衡实验证实了COSMO-RS筛选结果的可靠性,其中ChCl∶EG(1∶2)具有最高的分配系数和选择性系数,且黏度最低,被选定为最佳的低共熔溶剂。在25℃、ChCl∶EG(1∶2)与模型油质量比为1∶1时,ChCl∶EG(1∶2)对间甲酚萃取率高达98.41%,同时异丙苯夹带量仅为8.41%,并且具有良好的循环使用性能。     

Effect of posttreatment on morphology and properties of poly(ethylene‐co‐vinyl alcohol) microporous hollow fiber via thermally induced phase separation

Poly(ethylene‐co‐vinyl alcohol) (EVOH) hollow fiber membranes were prepared by thermally induced phase separation (TIPS) process. Water, methanol, and acetone were used to extract the diluents in the fibers, respectively. Bigger shrinkage of fibers during extractant evaporation was observed when water or methanol was used. Their interaction parameters with EVOH were calculated via Hansen solubility, respectively. The mechanism of hollow fiber volume shrinkage was discussed. It was found that affinity of the extractant with polymer was the critical factor except for the surface tension of extractant. Through the X‐ray diffraction analysis during extraction and evaporation, the crystallization behavior of the polymer was studied. From the SEM photos, it was observed that the volume shrinkage was derived from the collapse of porous structure. The fiber sample extracted by acetone had similar morphology with the sample freeze‐dried. The gas and water permeability were also measured and the results were coincident with the morphology of fibers and shrinkage data. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4106–4112, 2007     

Equilibrium studies on enantioselective extraction of oxybutynin enantiomers by hydrophilic β‐cyclodextrin derivatives

The enantioselective extraction of hydrophobic oxybutynin (OBN) enantiomers by hydrophilic β‐cyclodextrin (β‐CD) derivatives was studied. The efficiency of extraction depends strongly on a number of process variables such as types of organic solvents and β‐CD derivatives, concentration of selector, pH, and temperature. The experimental data were described by a reactive extraction model with a homogeneous aqueous phase reaction of R,S‐OBN with β‐CD. Important parameters of this model were determined experimentally. The physical distribution coefficients for molecular and ionic OBN were 4.96 × 10^?3 and 9.52, respectively. The equilibrium constants of the complexation reactions were 1770 and 1340 L/mol for S‐ and R‐OBN, respectively. By modeling and experiment, an optimal extraction condition with pH of 5 and HP‐β‐CD concentration of 0.1 mol/L was obtained with enantioselectivity (α) of 1.26, which was close to the theoretical maximum of 1.32 and performance factor (pf_i) of 0.036. The model was verified experimentally with excellent results. © 2011 American Institute of Chemical Engineers AIChE J, 2011     

知母总皂苷提取分离方法研究

研究了知母总皂苷的提取及分离工艺,探讨了提取剂、料液比、提取次数、回流时间对知母总皂苷提取率的影响,最后用AB-8大孔吸附树脂进行纯化。实验表明,最佳实验条件为:80℃下,以75%的乙醇为提取剂,按料液比1∶8和1∶6各提取一次,每次1 h,用AB-8大孔吸附树脂吸附,以80%乙醇洗脱,流速3 mL/min,提取率可达96.0%,纯度可达93.2%以上。     

Effects of transport and phase equilibrium on fast, nearly irreversible reactive extraction

Integration of reaction and separation can be exploited to drive reversible reactions in the direction of the desired product using multiphase flow contacting. In the case of nearly irreversible, fast reactions, however, the dynamics of the product have little influence on the reactor efficiency in say liquid-liquid reactive extraction. A similar intensification in reaction efficiency to reactive separation can be achieved by exploiting phase equilibrium or asymmetry in mass transfer rates of the reactants. Here, a model for two-layer biphasic flow and homogeneous reaction is proposed for co-current reactive extraction, demonstrating that localization and intensification of reaction occurs in the region between the entrance and crossover. Crossover occurs if the reactant in stoichiometric deficit preferentially populates the reacting phase due to sufficient imbalance in either mass transfer coefficients or phase equilibrium. We develop an infinite Peclet number (convection dominates over bulk diffusion) model that indicates that crossover occurs when

     

Electro‐membrane process for the separation of amino acids by iso‐electric focusing

BACKGROUND: Amino acids (AAs) are usually produced commercially using chemical, biochemical and microbiological fermentation methods. The product obtained from these methods undergoes various treatments involving extraction and electrodialysis (ED) for salt removal and AA recovery. This paper describes an electro‐membrane process (EMP) for the charge based separation of amino acids. RESULTS: Iso‐electric separation of AAs (GLU–LYS) from their mixture, using ion‐ exchange membranes (IEMs) has been achieved by an efficient and indigenous EMP. It was observed that electro‐transport rate (flux) of glutamic acid (GLU) at pH 8.0 (above its pI) was extremely high, while that for lysine (LYS) (pH 9.6) across the anion‐exchange membrane (AEM) was very low, under similar experimental conditions. Under optimum experimental conditions, separation of GLU from GLU–LYS mixture was achieved with moderate energy consumption (12.9 kWh kg^?1), high current efficiency (CE) (65%) and 85% recovery of GLU. CONCLUSIONS: On the basis of the electro‐transport rate of AA and membrane selectivity, it was concluded that the separation of GLU–LYS mixture was possible at pH 8.0, because of the oppositely charged nature of the two amino acids due to their different pI values. Moreover, any type of membrane fouling and deterioration in membrane conductivity was ruled out under experimental conditions. This work clearly demonstrates the great potential of EMP for industrial applications. Copyright © 2010 Society of Chemical Industry     

Kinetic study on reactive extraction of clorprenaline enantiomers with a combined chiral selector

This paper reports on the kinetic study on reactive extraction of clorprenaline (CPNL) enantiomers with isobutyl (d)-tartrate (DT) and boric acid (BA) as combined chiral selector in a Lewis cell, where exists an interfacial reaction involving three species: BA, DT, and CPNL enantiomers. The important factors that influence the kinetics of reactive extraction are investigated. Through multiple linear regression analysis of the experimental data, the order with respect to BA, CPNL, and DT of the interfacial reaction is 0.6, 0.8, and 0.8, respectively, and the total order of reaction is about 2.2. The forward rate constants have been calculated to be 2.476 × 10^–4 L^1.53/(mol^1.2 s) for (R)-CPNL and 1.349 × 10^–4 L^1.53/(mol^1.2 s) for (S)-CPNL.     

Preparation and characterization of a pseudo‐template imprinted polymer with a chirality‐matching monomer for the separation of cinchona alkaloids by high‐performance liquid chromatography

A hydroquinidine‐imprinted stationary selector with chiral recognition for cinchona alkaloids was prepared by bulk polymerization with (+)‐(2R,3R)‐N,N′‐diallyl‐L ‐tartardiamide as a functional monomer, and the recognition properties of the polymers for quinidine (QD) were analyzed with high‐performance liquid chromatography. By optimizing the preparation conditions and chromatographic conditions, such as the ratio of the mobile phase and flow rate, QD and quinine could be completely separated to the best resolution of 2.25. The chiral molecularly imprinted polymers (CMIPs) combined the virtues of traditional brush‐type chiral selectors with existing CMIPs. The results show a substantial synergistic effect between the chiral monomer and the chiral cavity of the resulting CMIPs in chiral recognition. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Influence of attapulgites on cure‐reaction‐induced phase separation in epoxy/poly(ether sulfone) blends

The influence of attapulgites (ATTs) on cure‐reaction‐induced phase separation in diglycidyl ether of bisphenol A/poly(ether sulfone) (PES) blends has been studied with scanning electron microscopy (SEM), transmission electron microscopy (TEM), optical microscopy, time‐resolved light scattering, and dynamic mechanical analysis at different ATT and PES concentrations. The SEM results show that the incorporation of a small amount of ATT into the blends can change the final phase morphology markedly and affect the secondary phase separation. The TEM results show that ATT particles are pinned down by the interfacial tension at the phase interfaces, and this slows the interfacial motion. In addition, the incorporation of a small amount of ATT particles can improve the modulus because of the increased interfacial interaction of the PES‐rich and epoxy‐rich phases. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Kinetics study on the reactive extraction of homophenylalanine enantiomers with BINAP-copper complex

This paper reports on the kinetics study of the reactive extraction of homophenylalanine (Hph) enantiomers with BINAP (2,2’-Bis(diphenylphosphino)-1,1’-binaphthalene)-copper complex (BINAP-Cu) as the chiral selector. The kinetic model was established based on the theory of interfacial chemical reactive extraction. Simultaneously, the effects of agitation speed, interface area, pH value of the aqueous phase, initial concentration of Hph enantiomers and initial concentration of BINAP-Cu on the specific rate of extraction were investigated. The forward rate constants of the reactions in reactive extraction process were found to be 6.16 × 10^?4 m^2.5mol^?0.5s^?1 for D-Hphe and 7.303 × 10^?4 m^2.5mol^?0.5s^?1 for L-Hphe.