Liquid-liquid Biphasic Systems Research Articles

TEMPO-Grafted Polystyrene/Polymethacrylate Organosiloxane Janus Nanohybrids as Efficient Pickering Interfacial Catalyst for Selective Aerobic Oxidation of Cinnamyl Alcohol.

The novel 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) groups immobilized on functional polymers or nanoparticles emerged as potential Pickering interfacial catalysts (PICs) for effective catalysis in biphasic systems. In this study, a snowman-shaped Janus-structured polymer with TEMPO-anchored nanohybrid particles (SM-JPP-TEMPO) was prepared and employed as a potential PIC in the Anelli-Montanari system for the selective oxidation of alcohol. The amphiphilic character of SM-JPP-TEMPO particles plays a dual role as an emulsifier and catalyst in the Pickering emulsion. As a result, it enables smaller droplets (102 μm) at the water-in-oil (W/O) interface and reduces the interfacial tension from 26.58 to 17.38 mN/m, which improves the stability of the Pickering emulsion system. This constructed Pickering emulsion microreactor offers a larger interface contact area and shortens the mass transfer distance of the substrate of cinnamyl alcohol, which significantly enhances the catalytic conversion at the Anelli-Montanari oxidation system, thus achieving remarkable conversion efficiency of (92.3%) with excellent selectivity (99%) in static (stirring-free) condition. It was found that the Janus nanohybrid catalyst (SM-JPP-TEMPO) enhanced 1.29-fold catalytic efficiency compared to the TEMPO grafted spherical polystyrene nanoparticle (PS-NPs-TEMPO) catalyst (72%). Moreover, after seven consecutive cycles, the Janus nanocatalyst (SM-JPP-TEMPO) maintained the conversion significantly. Hence, these results collectively highlight that the amphiphilic SM-JPP-TEMPO catalyst provides an efficient and eco-friendly strategy for the intensification of liquid-liquid biphasic reaction systems for potential applications in industries.

Microwave enhancement of extractions and reactions in Liquid-Liquid biphasic systems

Microwaves (MWs) are a powerful technology for electrifying chemical processing and can enable selective heating, which is impossible in conventional systems. This effect was recently ascribed to enhancing liquid–liquid reactive extractions in biomass derivative chemistry. Expanding upon prior research that showcased MW-induced temperature gradients and their optimization, this study delves into the impact of these gradients on extraction using a combination of experiments and simulations. The findings illustrate that the colder organic phase enforced by the MW heating leads to alterations in solute partitioning and phase behavior. Partitioning can be further tuned by adding salts or by carefully selecting solvents, as demonstrated via COSMO-RS calculations. The colder organic phase also leads to Rayleigh instabilities and active buoyancy-driven mixing. These effects, measured experimentally and simulated in COMSOL, can greatly enhance mass transfer rates in liquid–liquid systems. Under conditions reported in the literature, the MW enhancement to reactive extractions is minimal. Conditions that may lead to more impressive extractions and reactive extractions are suggested. Additionally, it's observed that temperature gradients retard byproduct formation.

Carbon black intercalation compound as catalyst for unprecedent phase-transfer-catalyzed nucleophilic substitution (SN2) in water

Carbon black intercalation compound was used for the first time as a heterogeneous phase-transfer-catalyst for SN2 type reaction of NaSCN with 4-nitrobenzyl bromide. The reaction proceeds in the presence of 5 mol% of catalyst with high efficiency in a liquid-liquid biphasic system (CHCl3/H2O), providing 98% conversion after only 4 h. Furthermore, an unprecedent efficient nucleophilic substitution was reported in water solution in the presence of the new catalyst, providing 95% yield in 8 h. The reaction is green, and the heterogeneous catalyst can be recovered and recycled without losing efficiency.

Phase equilibria insights into amine-water-NaCl interactions in liquid-liquid biphasic systems for temperature swing solvent extraction desalination

This study sheds light on the fundamental phenomena governing temperature swing solvent extraction (TSSE) desalination by investigating the influence of temperature on the equilibrium partitioning of water, salt, and solvent. The distribution of components across a range of temperatures and feed salinities typical to TSSE hypersaline desalination was examined for two amine solvents. A tradeoff between selectivity and productivity is established, providing a novel framework to assess TSSE performance. Salt was shown to be a key determinant in equilibrium partitioning by diminishing the ability of the solvent to extract water at lowered temperatures and salting-out amines from the aqueous phase. Na+ and Cl− ions consistently partition into the solvent phase in equimolar ratios. Analysis further reveals a linear correlation between the natural logarithms of salt activity coefficients and water contents of the organic phase. The two collaborating results suggest that water-ion interactions are more important than amine-ion interactions in the organic phase, resolving a critical gap in the understanding of salt transport. The findings of this study can provide important insights for the informed development of temperature swing solvent extraction for hypersaline desalination.

Green Process Design for Reductive Hydroformylation of Renewable Olefin Cuts for Drop‐In Diesel Fuels

CO2‐neutral fuels are a way to cleaner and more sustainable mobility. Utilization of bio‐syngas via Fischer‐Tropsch (FT) synthesis represents an interesting route for the production of tailormade biofuels. Recent developments in FT catalyst research led to olefin‐enriched products, enabling the synthesis of alcohol‐enriched fuels by reductive hydroformylation of the C=C bond. Several alcohols have already proven to be suitable fuel additives with favorable combustion behavior. Here, a hydroformylation‐hydrogenation sequence of FT‐olefin‐paraffin mixtures was investigated as a potential route to alcohols. A liquid‐liquid biphasic system with a rhodium/3,3’,3’’‐phosphanetriyltris(benzenesulfonic acid) trisodium salt (TPPTS) catalyst system was chosen for effective catalyst recycling. After optimizing reaction conditions with a model substrate consisting of 1‐octene and n‐heptane the conversion of an actual olefin‐containing C5‐C10 FT product fraction to alcohols in continuously operated processes for 37 h was achieved with a total turnover number of 23679.

Extraction and determination of synthetic food dyes using tetraalkylammonium based liquid-liquid extraction

Tetraalkylammonium based liquid-liquid biphasic systems (employing room-temperature ionic liquids tetraoctylammonium N-lauroylsarcosinate, TOALS, and tetrahexylammonium dihexylsulfosuccinate, THADHSS, as well as tetrahexylammonium bromide, THABr) were used for liquid-liquid extraction of synthetic food dyes followed by spectrophotometric determination. Dyes studied are Allura Red AC, Red 2G, Azorubine, and Fast Green FCF (all anionic). Both extraction to pre-synthesized ILs and to ILs formed in situ was studied. The effects of pH, ionic liquid volume, dye concentration, time of extraction/centrifugation and other factors were investigated and optimum conditions were established. Dispersive liquid-liquid microextraction (DLLME) in situ is based on a metathesis between two salts which are suppliers of cations and anions of IL. It was found that efficiency of in situ DLLME with the studied ILs strongly depends on the ratio between cation and anion suppliers (THABr and NaDHSS/ NaLS, resp.) and drops sharply if an excess of anion supplier is used. Liquid-liquid extraction system using THABr was found to be superior for preconcentration and spectrophotometric determination of Allura Red AC and Azorubine in food samples. Under optimal conditions, recovery of all analytes was nearly 100%. Linear calibration curves in the range of 0.05–4.95 mg L−1 for Allura Red AC and 0.05–2.00 mg L−1 for Azorubine were obtained. Detection limits based on 3Sb were 0.004 and 0.006 mg L−1 for Allura Red and Azorubine, respectively. The proposed method was applied to determination of Allura Red and Azorubine in beverage and Easter egg coloring set.

Surface Modification of Layered Perovskite Nanosheets with a Phosphorus Coupling Reagent in a Biphasic System.

Oleyl phosphate-modified HLaNb2O7· xH2O nanosheets (OP_HLaNb nanosheets) were prepared via phase transfer from an aqueous phase, comprising a dispersion of HLaNb2O7· xH2O (HLaNb) nanosheets, formed through the intercalation of tetrabutylammonium ion (TBA+) in the interlayer space of HLaNb and subsequent delamination, to a cyclohexane phase containing oleyl phosphate (OP, a mixture of monoester and diester). The modification of HLaNb nanosheets with OP was essentially completed within 3 days at a pH value of 2 or 4. Both infrared and solid-state 13C cross-polarization and magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of the OP_HLaNb nanosheets showed the presence of OP and/or related species and TBA+ on the HLaNb nanosheet surface. The solid-state 31P MAS NMR spectra of OP_HLaNb nanosheets exhibited new signals at -2 and 0 ppm, the former of which indicates the formation of Nb-O-P bonds. These whole data set obtained by complementary techniques clearly point out the modification of the HLaNb nanosheet surface by OP moieties causing a phase transfer. OP_HLaNb nanosheets showed higher dispersibility in cyclohexane than the OP_HLaNb_interlayer nanosheets, which were prepared via stepwise substitution reactions in the interlayers of HLaNb to achieve surface modification with OP and subsequent exfoliation in cyclohexane. The presence of TBA+ on the HLaNb nanosheets and the use of a liquid-liquid biphasic system were likely to improve the dispersibility. These results show that the preparation of OP-modified HLaNb nanosheets which could be well-dispersed in the cyclohexane phase was successful because of the use of a liquid-liquid biphasic system.

Recent Progress on Transition Metal Catalyst Separation and Recycling in ATRP.

Atom transfer radical polymerization (ATRP) is a versatile and robust tool to synthesize a wide spectrum of monomers with various designable structures. However, it usually needs large amounts of transition metal as the catalyst to mediate the equilibrium between the dormant and propagating species. Unfortunately, the catalyst residue may contaminate or color the resultant polymers, which limits its application, especially in biomedical and electronic materials. How to efficiently and economically remove or reduce the catalyst residue from its products is a challenging and encouraging task. Herein, recent advances in catalyst separation and recycling are highlighted with a focus on (1) highly active ppm level transition metal or metal free catalyzed ATRP; (2) post-purification method; (3) various soluble, insoluble, immobilized/soluble, and reversible supported catalyst systems; and (4) liquid-liquid biphasic catalyzed systems, especially thermo-regulated catalysis systems.

High temperature thermoelectric properties of PbTe prepared by high pressure method

Abstract Highly dispersed olive-like NiS particles were synthesized in a liquid-liquid biphasic system at room temperature, where nickel xanthate in organic solvents (toluene and benzene) and sodium sulfide in water solution were used as nickel and sulfide sources, respectively. NiS particles were formed at the stabilized phase interface. The structures, chemical composition and optical characteristics of the products were investigated by transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and ultraviolet-visible spectroscopy. The organic solvents obviously influenced the morphology of the NiS particles. The olive-like NiS with smooth surface and sharp ends was obtained at benzene/water interface, while spindle-like NiS particles with rough surface and circle ends were formed when using toluene as a solvent. Analogously, chainlike Bi2S3 nanowires were produced at chloroform/water interface. The effect of the experiment parameters including reaction time, solvent and concentration of reactants on the size and morphology of the products was discussed in detail and a possible formation mechanism was suggested.

Two-phase synthesis of olive-like NiS particles and chain-like Bi2S3 nanowires

Abstract Highly dispersed olive-like NiS particles were synthesized in a liquid-liquid biphasic system at room temperature, where nickel xanthate in organic solvents (toluene and benzene) and sodium sulfide in water solution were used as nickel and sulfide sources, respectively. NiS particles were formed at the stabilized phase interface. The structures, chemical composition and optical characteristics of the products were investigated by transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and ultraviolet-visible spectroscopy. The organic solvents obviously influenced the morphology of the NiS particles. The olive-like NiS with smooth surface and sharp ends was obtained at benzene/water interface, while spindle-like NiS particles with rough surface and circle ends were formed when using toluene as a solvent. Analogously, chainlike Bi2S3 nanowires were produced at chloroform/water interface. The effect of the experiment parameters including reaction time, solvent and concentration of reactants on the size and morphology of the products was discussed in detail and a possible formation mechanism was suggested.

Biotransformation of Indole to Indigo by the Whole Cells of Phenol Hydroxylase Engineered Strain in Biphasic Systems

Biotransformation of indole to indigo in liquid-liquid biphasic systems was performed in Escherichia coli cells expressing phenol hydroxylase. It was suggested that indole could inhibit the cell growth even at low concentration of 0.1g/L. The critical Log P for strain PH_(IND) was about 5.0. Three different solvents, i.e., decane, dodecane, and dioctyl phthalate, were selected as organic phase in biphasic media. The results showed that dodecane gave the highest yield of indigo (176.4mg/L), which was more than that of single phase (90.5mg/L). The optimal conditions for biotransformation evaluated by response surface methodology were as follows: 540.26mg/L of indole concentration, 42.27% of organic phase ratio, and 200r/min of stirrer speed; under these conditions, the maximal production of indigo was 243.51mg/L. This study proved that the potential application of strain PH_(IND) in the biotransformation of indole to indigo using liquid-liquid biphasic systems.

Two-Phase Synthesis of Monodisperse Silica Nanospheres with Amines or Ammonia Catalyst and Their Controlled Self-Assembly

A significant progress has recently been made in the synthesis of monodisperse silica nanoparticles less than 30 nm in diameter by using basic amino acids (e.g., lysine) as a base catalyst for hydrolysis of silicon alkoxide. Alternatively, a more versatile and economical amino acid-free method has been developed to synthesize uniform silica nanospheres (SNSs) with low polydispersity (<12%) in liquid-liquid biphasic systems containing tetraethoxysilane (TEOS), water, and primary amine (or ammonia) under precisely controlled pH conditions (pH 10.8-11.4). The diameter of the SNSs determined from scanning electron microscopy (SEM) can be tuned from ∼12 to ∼36 nm by simply changing the initial pH of the aqueous phase in the reaction mixtures. Furthermore, the as-synthesized sol was taken as the starting material for studying the influences of the type of base catalysts on the solvent evaporation-induced three-dimensional (3D) self-assembly of SNSs. X-ray diffraction (XRD) and nitrogen adsorption-desorption are used to characterize the degree of packing of the resulting 3D arrays. The assembled SNSs with large interparticle mesopores with the diameter of ca. 8.1 nm and low packing fraction of ca. 66.1% are observed upon solvent evaporation of as-synthesized sol in the presence of primary amine. This indicates that SNSs are loosely packed, compared with the packing fraction of 74% for a face-centered cubic array of ideal hard spheres. In contrast, with the aid of an organic buffer or lysine as additives, the assembly of SNSs having smaller mesopores (ca. 3.9 nm) and higher packing fraction of 70.5-71.5% are achieved. It is suggested that the chemical additives with the ability to maintain relatively strong repulsive interaction until the final stage of evaporation play a vital role in the fabrication of well-ordered SNSs arrays.

Estimation of Coalescence Parameters in an Agitated Extraction Column Using a Hybrid Algorithm

AbstractA method based on a genetic algorithm (GA) combined with Levenberg‐Marquardt (LM) method applicable to the population balance model for coalescence parameter estimation in a liquid‐liquid biphasic system is presented. The toluene/water system in a rotating disk contactor was taken as an example. Estimation methods for such a problem are often based on deterministic optimization models that are rather instable and divergent around a local minimum. To overcome these limitations, the present study involves the introduction of a semi‐stochastic method that is able to provide at first the estimation of coalescence parameters from the GA based on an inverse approach, exploiting the principle of GA. The LM algorithm was applied to ensure that the results are not restricted to a local minimum.

ChemInform Abstract: Multiphase Homogeneous Catalysis: Common Procedures and Recent Applications

AbstractReview: about 100 refs.

Whole-Cell Biocatalysis for 1-Naphthol Production in Liquid-Liquid Biphasic Systems

Whole-cell biocatalysis to oxidize naphthalene to 1-naphthol in liquid-liquid biphasic systems was performed. Escherichia coli expressing TOM-Green, a variant of toluene ortho-monooxygenase (TOM), was used for this oxidation. Three different solvents, dodecane, dioctyl phthalate, and lauryl acetate, were screened for biotransformations in biphasic media. Of the solvents tested, lauryl acetate gave the best results, producing 0.72 +/- 0.03 g/liter 1-naphthol with a productivity of 0.46 +/- 0.02 g/g (dry weight) cells after 48 h. The effects of the organic phase ratio and the naphthalene concentration in the organic phase were investigated. The highest 1-naphthol concentration (1.43 g/liter) and the highest 1-naphthol productivity (0.55 g/g [dry weight] cells) were achieved by optimization of the organic phase. The ability to recycle both free cells and cells immobilized in calcium alginate was tested. Both free and immobilized cells lost more than approximately 60% of their activity after the first run, which could be attributed to product toxicity. On a constant-volume basis, an eightfold improvement in 1-naphthol production was achieved using biphasic media compared to biotransformation in aqueous media.

Use of Ionic Liquids for the Diels‐Alder Reaction of Oleochemicals

Recently, ionic liquids have found increasing attention as new reaction media, especially for homogeneously catalyzed syntheses in liquid‐liquid biphasic systems. Their physical and chemical properties are very attractive and can be tuned by a proper choice of the organic cation as well as of the anion. This report presents the use of ionic liquids as reaction media and catalysts for the derivatization of long‐chain fatty acid esters by Diels‐Alder reaction.

Quantification of flotation activity by means of excess Gibbs free energies

Flotation activity is related to the Excess Gibbs Free Energies (G ex ) of the binary system, [adsorbed collector-water]. In this investigation, the studied variables are; activity coefficients, surface coverage by collector molecules (mole fraction) and absolute temperature. The Unifac method and principles based on liquid-liquid equilibria were used to calculate G ex values for twenty four different molecules. G ex values correlated well with flotation activity. Water interactions with N, S, O and organic functional groups of collector molecules were quantified. With isomorphous substitution, the effectiveness of substituents followed the order S>O>N and is interpreted in terms of partial and total miscibility in the liquid-liquid bi-phasic system.

Use of the electrically driven emulsion-phase contactor for a biphasic liquid-liquid enzyme system

An alternative approach to the operation of bioprocessing systems within non-aqueous environments would require the development of reaction systems that would provide effective interfacial contact between the biocatalyst, contained within an aqueous phase, and the organic phase containing the substrate. A biphasic liquid-liquid (BLL) reactor that provides for intimate liquid-liquid contact would be the most probable approach for this application. For the BLL reactions considered in this work, the overall effectiveness of the system will depend on both compatibility of the biocatalyst with the chemical species present and intrinsic reaction and interfacial transport phenomena typically involved with liquid-liquid operations. The focus of this article is to investigate the removal and oxidation of p-cresol dissolved in toluene by aqueous-phase horseradish peroxidase. Contacting of the liquid-liquid biphasic enzyme system is carried out in an advanced solvent extraction contacting device, the electrically driven emulsion-phase contactor (EPC).

Protein-protein interactions studied by counter-current distribution : I. Theoretical computations

Many biological macromolecules are known to interact either with themselves, with other macromolecules or with small compounds. A simple equilibrium method for detecting and quantifying these interactions is to study the mutual influence of the molecules on their respective counter-current distribution in liquid-liquid biphasic systems. The theoretical counter-current distribution patterns for the components in an interacting system, A + B ⇌ AB, have been calculated for two models in order to establish the boundary conditions and to optimize the experimental procedure. The patterns have been calculated for a range of association constants, partition coefficients and initial concentrations of the two reactants.