Toluene Water System Research Articles

Liquid–liquid two-phase flow in a wire-embedded concentric microchannel: Flow pattern and mass transfer performance

In this work, flow pattern and mass transfer of liquid–liquid two-phase flow in a wire-embedded concentric microchannel are studied using toluene–water system. Droplet flow, slug flow, oval flow and annular flow are observed in the wire-embedded concentric microchannel. The effects of embedded wires and physical properties on flow patterns are investigated. The embedded wire insert is conducive to the formation of annular flow. The flow pattern distribution regions are distinguished by the Caaq (capillary number)–Weorg (Weber number) flow pattern map. When Weorg＜0.001, slug flow is the main flow pattern, and when Weorg＞0.1, annular flow is the main flow pattern. Oval flow and droplet flow are between Weorg=0.001–0.1, and oval flow is transformed into droplet flow with the increase of Caaq. The effect of flow rate, phase ratio, initial acetic acid concentration, insert shape and flow patterns on mass transfers are studied. Mass transfer process is enhanced under annular flow conditions, the volumetric mass transfer coefficient is up to 0.36 s–1 because of the high interfacial area and interface renewal rate of annular flow.

The Solution Properties of Polymethacrylate Molecular Brushes with Oligo(ethylene glycol) and Oligo(propylene glycol) Side Chains.

The properties of polymer brushes based on three macromonomers were investigated in aqueous and organic solutions. Methacrylic monomers with different compositions of the oligo(oxyalkylene) substituents and arrangements of the oligo(ethylene glycol) and oligo(propylene glycol) blocks were used for the synthesis of polymers. There were methoxy [oligo(ethylene glycol)10.3-block-oligo(propylene glycol)4.7] methacrylate, methoxy [oligo(propylene glycol)8.3-block-oligo(ethylene glycol)6.6] methacrylate, and methoxy oligo(propylene glycol)4.2 methacrylate. Molecular brushes were investigated by the methods of molecular hydrodynamics and optics in dilute solutions in acetonitrile, chloroform, and water. The peculiarities of behavior of poly[oligo(oxyalkylene) methacrylates] in aqueous solutions and water-toluene systems have been found; in particular, the solubility of the polymers in water and organic solvents, the polymers equilibrium distribution between the phases, and the surface activity in the water-toluene system have been established. The thermo-responsibility in aqueous solutions and values of a critical concentration of micelle formation were shown. Depending on the arrangement of blocks in the side chains of molecular brushes, they are characterized by different intramolecular density.

Hydrodynamics and mass transfer of liquid-liquid two-phase flow in circular milli-channels: Sizing-up effect

Background: Microfluidic is one of the most promising technologies for safety production in chemical industry while scale-up is a major challenge for its industrialization. Methods: In this work, hydrodynamics and mass transfer of liquid-liquid two-phase flow in different circular milli-channels were experimentally and numerically studied to investigate the sizing-up effect. Significant findings: Slug flow was observed in toluene-water system and the droplet length was measured. The results showed shorter droplets tended to present under higher flow rates, inlet mode one and smaller T-mixers. The buoyancy exerted on the toluene phase accelerated droplet detachment. For n-butanol-water system, a repetition of ‘parallel flow - annular flow’ was observed due to the prominent gravitational effect. The flow was asymmetric and the phenomenon was especially notable in the serpentine channel with a larger diameter. The detailed velocity field was demonstrated by numerical simulation. Mass transfer enhancement was observed in smaller channels and serpentine channels, resulting from shorter diffusion distance and secondary flow, respectively.

Study on mass transfer in reactive liquid-liquid systems

This work examines the mass transfer in reactive liquid-liquid systems applying the dynamic concentration gradient theory (CGT). The CGT is based on a square gradient approach delivering an expression for the Gibbs energy of an inhomogeneous system as basis for the mass transfer in a two-phase system. For this work, the CGT was combined for the first time with a reaction kinetics model to model the reactive mass transfer. The model was validated by experiments. As model reaction the reversible diacetone alcohol formation in a water-toluene system was chosen. To parameterize the Gibbs excess energy model, phase equilibria were measured and furthermore, the predictive power of the model to calculate interfacial tension in equilibrium was also checked by own experiments. To analyze the mass transfer in liquid-liquid systems the model prediction was compared to experimental data from Nitsch-cell experiments. It was found that the model predictions are in excellent agreement to the forward reaction predictions as well as to the backward reaction.

Molecular Dynamics study of the effect on the interfacial activity of Alkylamine-Modified graphene oxide

Several experimental studies have shown that chemical modification of graphene oxide with n-alkylamines allow to control its interfacial activity in oil–water systems, altering its dispersibility and favoring the formation of emulsions. However, due to the complexity of its chemical structure and experimental limitations, the emulsification mechanism and interfacial properties have not been fully understood. In order to understand the behavior at the oil-water interface of alkylamine functionalized Graphene Oxide (GO) based materials, in this research we evaluated the interfacial activity of GO functionalized with different alkylamines (aGO) with different aliphatic chain lengths of 1, 3, 5, 7, 9 and 12 carbon atoms by Molecular Dynamics simulations. The dispersibility of the GO-based materials was analyzed and it was found that the Hydrophilic-Lipophilic Balance (HLB) of the GO can be controlled with the alkylamine chain length, making the GO more hydrophobic as the aliphatic chain length of the alkylamines becomes longer. Alkylamine chains bonded on the GO structure were capable to modifying the orientation relative to the Toluene/Water interface, going from parallel for the GO case to orthogonal for the aGO nanosheets, adopting a “head–tail” configuration due to the hydrophobic effect between the aliphatic chains and the Water molecules. Simulations also revealed that synergistic effect of aGO can decrease the interfacial tension of the Toluene-Water system as the aliphatic chain length and number of sheets increase obeying the Traubés rule, indicating a behavior like molecular surfactant, where the IFT of the system decreases as the amount of surfactant increases.

Study of the water-oil interfacial activity of amino-modified graphene oxide

The interfacial properties of Graphene oxide (GO) based materials have been widely studied in emulsification processes. The 2D chemical structure and high reactivity of Graphene Oxide (GO) allows the properties modification as wettability and dispersibility. Furthermore, the functionalized GO has been tested as a surfactant agent; however, little or nothing is known about its mechanism of action. Here, we investigated the interfacial activity of amine-modified GO in a water-toluene system. To consider the effect of the aliphatic chain length, GO was functionalized by amidation reaction and nucleophilic substitutions with n-propylamine (GO@3 C) and n-dodecylamine (GO@12 C). The covalent functionalization of GO was confirmed by FTIR spectroscopy, Raman spectroscopy, XPS spectroscopy, XRD and their morphology were observed by Scanning Electron microscopy. Results showed that the chemical modification of GO with n-alkylamines can decrease the Interfacial Tension (IFT) of the water-toluene system as the nanomaterial concentration increase, like a molecular surfactant that obey the Traube´s rule. Wettability of the materials it was also determined by the sessile drop method, revealing that the GO hydrophobicity increases as the length of the aliphatic chain becomes longer. Characteristics of the emulsion droplets were determined by micrograph analysis, and it was revealed that the diameter size, stability, and kind of emulsion can be changed depending on the type of GO functionalization.

Pharmacokinetics-Driven Evaluation of the Antioxidant Activity of Curcuminoids and Their Major Reduced Metabolites-A Medicinal Chemistry Approach.

Curcuminoids are the main bioactive components of the well-known Asian spice and traditional medicine turmeric. Curcuminoids have poor chemical stability and bioavailability; in vivo they are rapidly metabolized to a set of bioreduced derivatives and/or glucuronide and sulfate conjugates. The reduced curcuminoid metabolites were also reported to exert various bioactivities in vitro and in vivo. In this work, we aimed to perform a comparative evaluation of curcuminoids and their hydrogenated metabolites from a medicinal chemistry point of view, by determining a set of key pharmacokinetic parameters and evaluating antioxidant potential in relation to such properties.Reduced metabolites were prepared from curcumin and demethoxycurcumin through continuous-flow hydrogenation. As selected pharmacokinetic parameters, kinetic solubility, chemical stability, metabolic stability in human liver microsomes, and parallel artificial membrane permeability assay (PAMPA)-based gastrointestinal and blood-brain barrier permeability were determined. Experimentally determined logP for hydrocurcumins in octanol-water and toluene-water systems provided valuable data on the tendency for intramolecular hydrogen bonding by these compounds. Drug likeness of the compounds were further evaluated by a in silico calculations. Antioxidant properties in diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and oxygen radical absorbance capacity (ORAC) assays were comparatively evaluated through the determination of ligand lipophilic efficiency (LLE). Our results showed dramatically increased water solubility and chemical stability for the reduced metabolites as compared to their corresponding parent compound. Hexahydrocurcumin was found the best candidate for drug development based on a complex pharmacokinetical comparison and high LLE values for its antioxidant properties. Development of tetrahydrocurcumin and tetrahydro-demethoxycurcumin would be limited by their very poor metabolic stability, therefore such an effort would rely on formulations bypassing first-pass metabolism.

Molecular dynamics simulation of the magnetic field influence on the oil-water interface

In this study, by using molecular dynamics simulations the effects of applying an external magnetic field on the interfacial tension of water-toluene system are investigated in the presence of asphaltenes molecules. In this paper, we present a modified velocity-Verlet algorithm that enables the NAMD source code to perform the magnetic field force as a new feature. The results of the simulations demonstrate that performing the magnetic field results in approximately 25% reduction in IFT. The reported results in the present investigation clarify the basic mechanisms for the effectiveness of the magnetic field on the interfacial behavior. The obtained result denotes that the number of hydrogen bonding between water and asphaltenes molecules increases when the magnetic field imposes to the interfacial system. The finding from this study will not only result in deep understanding of the magnetic treatment in the petroleum processing, but will also provide information for many other industrial applications including the liquid interface.

FEATURES OF MOLECULAR AGGREGATION OF BLOCK COPOLYMER ON BASE OF STYRENE AND POLYETHYLENE GLYCOL IN SOLUTIONS

This article focuses on the study of behavior of macromolecules of block copolymer on the base of styrene and polyethylene glycol in toluene media. Unique property of block copolymers is the ability of chemical heterogeneous blocks to phase separation. This process leads to the formation of micelle similar structures in selective solvents. These aggregates have the core from soluble block and the micelles capsule from insoluble block. Similar structures (reverse micelles) would be used for the purpose of stabilization of metal organosols. In this work aggregative stable reverse micelles in such systems as "toluene - water" and "toluene - methanol" have been prepared. Block copolymer of styrene and polyethylene glycol was applied as stabilizer in solutions with polymer concentration from 2.5 g/ 100 ml to 1 g/ 100 ml. Block copolymer has been synthesized by means of isocyanate cure on the end hydroxyl groups. Its structure has been confirmed by differential calorimetry spectroscopy (DSC) method. Dimension of formed particles has been determined by methods of sedimental turbidimetry and dynamic light scattering (DLS). Existence of both individual macromolecules and molecular aggregates in initial solutions has been established by DLS method. It has been found that dimensional homogeneity of organosol particles enlarges with the increase in dispersed phase content to 10 mass. %. At that, the size of the micelles in presence methanol is less than in water presence. Particles size also depends on polymer concentration in solution. The sizes of micelles in both systems increase with increasing concentration of the block copolymer, and with an increase in the content of the dispersed phase, a gradual decrease in their sizes is observed. It was shown that the sedimentation turbidimetry method does not reflect the behavior of the copolymer molecules in solutions, which results in a large scatter of data on the determination of particle sizes of the organosol in the toluene-water system with a water content of less than 5 masses. % . Based on the data obtained, it is assumed that micelles stabilized by a block copolymer based on styrene and polyethylene glycol can be used to introduce metal particles into them, followed by the formation of a metal layer on a solid surface.

Effects of nanoparticles on the drop behavior in the Oldshue-Rushton extraction column by using central composite design method

Abstract The experimental conditions for the determination of drop size and size distribution in the presence of silica nanoparticles (0.025 and 0.05 wt%) were studied by using the pilot plant Oldshue-Rushton extraction column. The effects of the three parameters such as rotor speed, dispersed phase flow rate as well as continuous phase flow rate were investigated by means of the central composite design (CCD), which is a subcategory of response surface methodology (RSM). The experiment was carried out by using toluene-water system and the results indicated that the nanoparticles reduce the Sauter mean drop size in the extraction column, albeit with a slight variation in the drop size distribution observed in the column. The operating parameters and the drop size is correlated by using central composite design and then tested on the basis of the goodness-of-fit statistics by the analysis of the variance. A new family of the probability distribution function based on the principle of the pre-exponential term to the maximum entropy method was studied for the prediction of drop size distribution. As a result, we found that MEP and pre-exponential term of MEP can provide a better alternative for the prediction of drop size distribution.

New correlations for slip velocity and characteristic velocity in a rotary liquid–liquid extraction column

In this research work, the hydrodynamic behavior of a Kühni extraction column has been investigated for determination of slip velocity and characteristic velocity for three different liquid–liquid systems with and without mass transfer conditions and toluene–water system with the presence of silica nanoparticles. The effects of the agitation speed, dispersed as well as continuous phase velocity, and interfacial tension were studied. The findings revealed that an increase in agitation speed and continuous phase velocity led to the reduction of slip velocity while it increased with increasing dispersed phase velocity. More buoyancy and faster upward movement of larger drops accelerate the slip velocity in the dispersed to continuous phase mass transfer condition as compared with the case of no mass transfer. In addition, the slip velocity decreased in the experimental conditions with nanoparticles because of the decrease in Sauter mean drop diameter and the increase in the holdup. Empirical correlations for prediction of slip and characteristic velocities are recommended. The results of the proposed correlations were compared with the experimental data obtained from the literature and the present investigation. Findings of this study demonstrated that the proposed correlations gave accurate predictions for slip velocity and characteristic velocity.

Modification of TiO2 Nanoparticles with Oleyl Phosphate via Phase Transfer in the Toluene-Water System and Application of Modified Nanoparticles to Cyclo-Olefin-Polymer-Based Organic-Inorganic Hybrid Films Exhibiting High Refractive Indices.

Oleyl-phosphate-modified TiO2 nanoparticles (OP_TiO2) were prepared via phase transfer from an aqueous phase containing dispersed TiO2 nanoparticles to a toluene phase containing oleyl phosphate (OP, a mixture of monoester and diester), and employed for the preparation of OP_TiO2/cyclo-olefin polymer (COP) hybrid films with high-refractive indices. The modification of TiO2 by OP was essentially completed by reaction at room temperature for 8 h, and essentially all the TiO2 nanoparticles in the aqueous phase were transferred to the toluene phase. The infrared and solid-state 13C cross-polarization and magic-angle spinning (CP/MAS) NMR spectrum of OP_TiO2 showed the presence of oleyl groups originating from oleyl phosphate. The solid-state 31P MAS NMR spectrum of OP_TiO2 exhibited new signals at -1.4, 2.1, and 4.8 ppm, indicating the formation of Ti-O-P bonds. CHN and inductively coupled plasma analyses revealed that the major species bound to the TiO2 surface was tridentate CH3(CH2)7CH═CH(CH2)8P(OTi)3. These results clearly indicate that the surfaces of the TiO2 nanoparticles were modified by OP moieties via phase transfer. OP_TiO2/COP hybrid films exhibited excellent optical transparency up to 19.1 vol % TiO2 loading, and the light transmittance of the hybrid films with 19.1 vol % TiO2 loading was 99.8% at 633 nm. The refractive index of these hybrid films rose to 1.83.

Ex situ Cu(0) nanoparticle mediated SET-LRP of methyl methacrylate/styrene-methyl methacrylate in a biphasic toluene–water system

Cu(0) nanoparticles mediated SET-LRP of methyl methacrylate/styrene-methyl methacrylate in biphasic toluene–water system.

Quasi-equilibrium distribution of pristine fullerenes C60 and C70 in a water–toluene system

An improved technique of the ultrasound-assisted reversible liquid–liquid transfer of pristine (unmodified) C60 and C70 fullerenes between organic solutions and aqueous fullerene dispersions (AFD; another notation in general use, nC60, nC70) without any additional reagents (media modifiers) was developed. To our knowledge, this is the first report of such a fullerene transfer from an AFD to an organic phase. Based on the observation of this fullerene reversible transfer, their distribution between the aqueous and organic phases was considered. A quasi-equilibrium transfer mechanism was proposed, which makes it possible to estimate distribution constants, KD, as 6 and 2, for C60 and C70 respectively, in a water–toluene system. Under the optimum conditions, AFDs of C60 and C70 with the concentrations 180 ± 20 and 70 ± 20 μM, respectively, were obtained from the corresponding solutions in toluene. Based on UV/vis spectroscopy, total organic carbon, headspace GC–MS, and MALDI measurements, a reliable analytical procedure to measure fullerene concentrations and to monitor the concentration of residual toluene in AFDs was proposed. AFDs of a mixture of fullerenes C60 and C70 were characterized by the developed technique.

HLD–NAC and the Formation and Stability of Emulsions Near the Phase Inversion Point

It is well-known that surfactant–oil–water (SOW) emulsions undergo substantial changes in drop size (10-fold or more) and stability (up to 4 orders of magnitude) near the phase inversion point. Predicting these changes is important in numerous applications. However, the complex connection between composition, formulation properties, and hydrodynamic conditions limits the ability to predict the outcome of emulsification and demulsification processes. To address this gap, the hydrophilic–lipophilic deviation (HLD) was used to quantify the proximity to the inversion point, considering the composition of the formulation, temperature, and electrolyte concentration. The net-average-curvature (NAC) equations combined with the HLD predicted the density, interfacial tension, interfacial rigidity, and viscosity for the sodium dihexyl sulfosuccinate (SDHS)–toluene–water system. The predicted properties were incorporated in hydrodynamic models to predict the initial emulsion drop size. The calculated properties and i...

Interfacial properties of asphaltenes at toluene-water interfaces.

Asphaltenes are "n-alkane insoluble" species in crude oil that stabilize water-in-oil emulsions. To understand asphaltene adsorption mechanisms at oil-water interfaces and coalescence blockage, we first studied the behavior in aliphatic oil-water systems in which asphaltenes are almost insoluble. They adsorbed as monomers, giving a unique master curve relating interfacial tension (IFT) to interfacial coverage through a Langmuir equation of state (EoS). The long-time surface coverage was independent of asphaltene bulk concentration and asymptotically approached the 2-D packing limit for polydisperse disks. On coalescence, the surface coverage exceeded the 2-D limit and the asphaltene film appeared to become solidlike, apparently undergoing a transition to a soft glassy material and blocking further coalescence. However, real systems consist of mixtures of aliphatic and aromatic components in which asphaltenes may be quite soluble. To understand solubility effects, we focus here on how the increased bulk solubility of asphaltenes affects their interfacial properties in comparison to aliphatic oil-water systems. Unlike the "almost irreversible" adsorption of asphaltenes where the asymptotic interfacial coverage was independent of the bulk concentration, an equilibrium surface pressure, dependent on bulk concentration, was obtained for toluene-water systems because of adsorption being balanced by desorption. The equilibrium surface coverage could be obtained from the short- and long-term Ward-Tordai approximations. The behavior of the equilibrium surface pressure with the equilibrium surface coverage was then derived. These data for various asphaltene concentrations were used to determine the EoS, which for toluene-water could also be fitted by the Langmuir EoS with Γ∞ = 3.3 molecule/nm(2), the same value as that found for these asphaltenes in aliphatic media. Asphaltene solubility in the bulk phase only appears to affect the adsorption isotherm but not the EoS. Further support for these observations is provided by dilatational rheology experiments for the EoS and contraction experiments in which desorption to the equilibrium surface pressure was observed.

Palladium(ii) complexes containing ONO tridentate hydrazone for Suzuki–Miyaura coupling of aryl chlorides in aqueous-organic media

Robust and recyclable pincer type palladium(ii) complexes for Suzuki–Miyaura coupling of challenging aryl chlorides in aqueous-organic media.

Alkaloids of the flora of Siberia and Altai: XX. Synthesis of 5-aryl(hetaryl)-substituted anthranilic acid esters

Cross-coupling of methyl 2-acetylamino-5-bromobenzoate and 5′-bromolappaconitine with aryl-, furyl-, pyridyl-, and 5-acetylthiophen-2-ylboronic acids or 1-(2-fluoroquinolin-3-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane gave the corresponding 5-aryl(hetaryl)-substituted anthranilic acid derivatives. The use of the two-phase toluene-water system as reaction medium and addition of tetrabutylammonium bromide allows the cross-coupling to be accomplished under mild conditions. The catalytic system Pd(dba)2-AsPh3 was found to be efficient in the cross-coupling of methyl 2-acetylamino-5-bromobenzoate with furyl- and pyridylboronic acids, whereas the system Pd(OAc)2-(o-Tol)3P ensured good results in the reactions of 5′-bromolappaconitine with hetarylboronic acids. Facile esterification at the C8-OH and C9-OH groups of the aconitane skeleton was observed in the reactions of 5′-bromolappaconitine and 5′-phenyllappaconitine with phenylboronic acid. 5′-Bromo-8,9-O-(phenylboranediyl)lappaconitine under the Suzuki reaction conditions underwent hydrolysis of the boronic ester moiety with formation of the cross-coupling product of 5′-bromolappaconitine with phenylboronic acid.

Mesoporous Nb2O5 as solid acid catalyst for dehydration of d-xylose into furfural

The acid-catalyzed dehydration of d-xylose to furfural has been investigated in a biphasic water–toluene system, using a mesoporous Nb2O5 catalyst prepared by a neutral templating route. The catalytic behavior was compared with a commercial Nb2O5. Materials were characterized by XRD, XPS, TEM, NH3-TPD, Raman spectroscopy and N2 sorption. The d-xylose conversion and furfural yield over the mesoporous niobia were found to increase with reaction temperature and time, in such a way that at 170°C and 90min, a d-xylose conversion and a furfural yield were higher than 90% and 50%, respectively. However, the commercial crystalline niobia displayed a low activity. The stability of the mesoporous catalyst has been demonstrated by XRD and N2 sorption, and corroborated by the absence of significant niobium leaching in solution.

A combined lossy capacitor population balance model (LCPBM) for calculating the influence of frequency on electric field enhanced coalescence in a static-mixer settler setup

In this work a combined lossy capacitor population balance model (LCPBM) is developed to predict the effect of a square wave frequency on electric-field coalescence (drop size) in a static-mixer settler setup for the caprolactam–toluene–water system. The static-mixer is used to mix the organic and aqueous phases. The electric field is applied by placing insulated electrodes at the end of the static-mixer. The electrical-circuit model of the system is based on the lossy capacitor model where the insulation and the dispersion are considered as leaky dielectrics. The charge and the electric field are determined from the electrical-circuit model and coupled in the hydrodynamic equation to calculate the velocities of drops. The velocities are in turn used in the population balance model (PBM) to determine the time evolution of the drop size. Three approaches are used to calculate the electrical force and the charge on the drops from the circuit model: (1) the Bailes′ charge hypothesis where the drops pick their charge from the free dispersion–insulation interfacial charge, and the electrical force calculated based on electrophoretic contribution, (2) the electrical force determined from the Taylor–Melcher leaky dielectric model considering the electrical force due to the free charge and the force due to the difference in dielectric permittivity's of the dispersion and insulation, and (3) by accounting for the free charge convection by the fluid motion which results in equal redistribution of the polarization charge between the dispersion and the insulation. The (LCPBM) model was validated by measuring drop sizes using a square wave of 0.4kV/cm and frequencies between 3 and 100Hz for two flowrates. With all approaches, the mean sauter diameters were calculated within 10% relative error at lower frequencies for both flowrates. At higher frequencies of 50Hz and 100Hz, a 20% relative error was obtained for the first approach. A better prediction within 10% was found for the second and third approaches with the later approach giving the best prediction.