Water-benzene System Research Articles

DPD Parameters Estimation for Simultaneously Simulating Water-Oil Interfaces and Aqueous Nonionic Surfactants.

The outcome of a coarse-grained simulation within the dissipative particle dynamics framework strongly depends on the choice of the repulsive parameter between different species. Different methodologies have been used in the literature to determine these parameters toward reproducing selected experimental system properties. In this work, a systematic investigation on possible procedures for estimating the simulation parameters is conducted. We compare methods based on the Hildebrand and the Hansen solubility parameter theories, mapped into the Flory-Huggins model. We find that using the Hansen solubility parameters it is possible to achieve a high degree of coarse graining, with parameters that yield realistic values for the interfacial tension. The procedure was first applied to the water/benzene system and then validated for water/ n-octane, water/1,1-dichloroethane, water/methyl cyclohexane, and water/isobutyl acetate. In all these cases, the experimental interfacial tension could be reproduced by adjusting a single correction factor. In the case of the water-benzene system, the dissipative particle dynamics parameters derived using our approach were able to simultaneously describe both the interfacial tension and micellar properties of aqueous nonionic surfactants representative of the octyl poly(ethylene oxide) C8H17O(C2H4O)mH family. We show how the parameters can be used, within the dissipative particle dynamics framework, to simulate the water/oil interface in the presence of surfactants at varying concentrations. The results show, as expected, that as the surfactant concentration increases, the interfacial tension decreases, and micelles form in bulk water.

Catalytic way of transforming 2,3-dimethylphenol to para-quinone with the use of vanadium-containing heteropoly acids

2,3-Dimethyl-p-benzoquinone (2,3-Me2BQ) is a valuable chemical that is applied as a soft oxidizing and dehydrogenating agent and also as a synthon in preparing different complex products including pharmaceutical and biochemical substances. Keggin- and modified-type aqueous solutions of Mo-V-phosphoric heteropoly acids (Mo-V-P HPAs) with the gross compositions H3+xPMo12-xVxO40 (HPA-x) and HaPzMoyVx’Ob (HPA-x’), respectively, possessing high oxidation potential and simplicity of regeneration can serve as effective soft oxidants for obtaining such para-quinone from 2,3-dimethylphenol (2,3-Me2P). The synthesized HPA catalysts with different vanadium content were characterized by a number of analysis techniques, such as 31P and 51V NMR spectroscopy, potentiometry, titrimetry, and pH measurement. It was found that the predominant formation of 2,3-Me2BQ instead of corresponding diphenoquinone (DPQ) at one-electron oxidation is achieved by a consecutive optimization of reaction conditions, the most important among them being organic solvent and molar ratio of vanadium(V) to substrate. As was shown, the substitution of HPA-x by HPA-x’ allows one to increase the quinone selectivity and to decrease the optimal molar ratio of vanadium(V) to substrate. The highest yield of the desired quinone (97%) at total substrate conversion was obtained by using the biphasic water-benzene system at molar vanadium(V) to substrate ratio of 12. The temperature of 50°C and an inert atmosphere were established to be the optimal reaction conditions. The aqueous HPA-10′ solution including the highest content of VO2+ ions proved to be the most efficient catalyst among investigated HPAs. Carrying out catalyst regeneration at a separate stage provides the preservation of its activity and selectivity at the initial level for at least ten cycles.

A potential surface for the interaction between water and coronene as a model for a hydrophobic surface

The potential energy surface for the interaction of a coronene molecule, as a model for a graphitic sheet, with a water molecule over its central ring has been calculated at the DFT and MP2 levels. The lowest energy orientation has both hydrogen atoms of the water pointing down symmetrically towards the coronene surface; this is also the preferred geometry for circumcoronene, C54H18. This is different from the water–benzene system, where the minimum is asymmetric, with one hydrogen pointing towards one of the carbon atoms in the ring. The coronene–water interaction energies were parameterized as a function of the Euler angles that describe the orientation of the water molecule and the distance between the oxygen atom and the coronene plane. The symmetry and distance dependence of the angular components were used to determine the physical origin of each term.

Computer Simulation Investigation of the Water−Benzene Interface in a Broad Range of Thermodynamic States from Ambient to Supercritical Conditions

The dependence of the properties of the water-benzene system on the thermodynamic conditions in a broad range of temperatures and pressures has been investigated by computer simulation methods. For this purpose, Monte Carlo simulations have been performed at 23 different thermodynamic states, ranging from ambient to supercritical conditions. The density profiles of the water and benzene molecules have been determined at each of the thermodynamic states investigated. Information on the dependence of the mutual solubility of the two components in each other as well as of the width of the interface on the temperature and pressure has been extracted from these profiles. The width of the interface has been found to increase with increasing temperature up to a certain point, where it diverges. The temperature of this divergence corresponds to the mixing of the two phases. The determination of the critical mixing temperature at various pressures allowed us to estimate the upper critical curve, separating the two-phase and one-phase liquid systems, of the phase diagram of the simulated water-benzene system. In analyzing the preferential orientation of the interfacial molecules relative to the interface, it has been found that the main orientational preference of the benzene molecules is to lie parallel with the plane of the interface, and the water molecules penetrated deepest into the benzene phase prefer to stay perpendicular to the interface, pointing by one of their O-H bonds almost straight toward the benzene phase, whereas the waters located at the aqueous side of the interface are preferentially aligned parallel with the interfacial plane. Although the strength of the observed orientational preferences decreases rapidly with increasing temperature, the preferred orientations themselves are found to be independent of the thermodynamic conditions. Remains of the orientational preferences of the molecules are found to be present up to temperatures as high as 650 K. The analysis of the relative orientation of the neighboring water-benzene pairs has revealed that the radius of the first hydration shell of the benzene molecules is independent of the thermodynamic conditions, even if the system consists of one single phase. It has been found that the nearest water neighbors of the benzene molecules are preferentially located above and below the benzene ring, whereas more distant water neighbors, belonging still to the first hydration shell, prefer to stay within the plane of the benzene molecule. In the two-phase systems the dipole vector of the nearest waters has been found to be preferentially perpendicular to the vector pointing from the center of the benzene molecule to the water O atom.

Divinyl Sulfoxide: XI. Selective Addition of Carbonodithioate Anions to Divinyl Sulfoxide in the Water-Benzene System

Selective monoaddition of carbonodithioate anions to divinyl sulfoxide gives rise to O-alkyl S-[2-(vinylsulfinyl)ethyl] carbonodithioates [ROC(S)SK, R = Et, Bu; 42–50°C, 6 h, NaHCO3, aqueous benzene].

Complexes of palladium(II) and platinum(II) with the PW 11O 7−39 heteropolyanion as catalytically active species in benzene oxidation

Aqueous solutions prepared from Pd(H 2O) 2+ 4 and PtCl 2− 4 with heteropolytungstate PW 11O 7− 39 at the Pd(II) or Pt(II) to PW 11 ratio from 1 to 8 and pH 2 and 4 have been characterized by means of UV-VIS and IR spectroscopy and 31P and 195Pt NMR. Three types of complexes have been detected in Pd(II) containing solutions. Two of them, [PW 11O 39Pd] (1) and [PW 11O 39PdOPdO 39W 11P] (2) had sharp peaks at δ 1 −13.2 and δ 2 −12.8 ppm in 31P NMR spectra. Possessing a broad signal at about − 13 ppm, complex (3) represented a water-soluble oligomeric Pd(II) hydroxide stabilized by the heteropolytungstate. The complex of type (1) (PW 11O 39Pt) was predominant in solutions of Pt(II). The Pd(II) complexes proved capable to catalyze the oxidation of benzene into phenol with a mixture of O 2 and H 2 gases in a two-phase water-benzene system at the temperature of 10 to 40°C. The yield of phenol for 1 h depended on the Pd(II) to PW 11 ratio and on pH and reached a maximum at an O 2 H 2 ratio equal to 2. The catalytic action was attributed mainly to complexes (1) and (2). Under the reaction conditions, these complexes have been found to be reduced into Pd(0) species which readily activate dioxygen and are stabilized in solution by heteropolytungstate. Pt(II) containing systems were one order of magnitude less active than Pd(II) containing ones.

素材小特集ＩＩＩ ： 素材製造プロセシング 水‐油界面におけるエマルジョンの生成と相分離

Interfacial tensions between water and some organic solvents were measured by the pendant drop method. Interfacial properties obtained in the present study were in agreement with the previous data. Effect of additions of some extractants on the interfacial tensions in the systems were also investigated. An ability of lowering the interfacial tensions between water and some organic solvents became strong in the order of D2EHPA, MIBK and TBP.Emulsion formation and phase separation behaviors in the systems were directly observed and recorded by a video camera. Minimum stirring powers to form an emulsion in the present study systems were found to be related with the interfacial tensions as shown in following equation (1).L=10 (γ-85.8/24.7)...(1)L: minimum stirring power to obtain emulsion stateγ: interfacial tensibn in water-organic solvent system On the other hand, phase separation behaviors were not simple. Disappearance times of the emulsions after stopping the stir were independent on the interfacial tensions in a water-benzene system. Two different linear relationships between the disappearance time and the interfacial tension were obtained in a water-kerosene and a water-hexane system, respectively.

Emulsion Polymerization of 2, 6-Xylenol Catalyzed by Copper-Partially-Quaternized Poly(vinylpyridine) Complex

2, 6-Xylenol (XOH) was oxidatively polymerized by Cu-partially-quaternized poly(vinylpyridine) (QPVP) complexes in a water-benzene system, the catalytic effects of the polymer-ligand and the mechanism of the polymerization were discussed. The Cu-QPVP complexes were soluble in water and the QPVP chelate which is formed above pH 5 was relatively stable in the range of pH 5, ---10. The oxidation was influenced by the pH of aqueous phase; the main product was biphenoquinone below pH 7, and was poly(phenyleneoxide) above pH 7. The maximum of the polymer yield was observed at pH 9; this fact is because of the following changes with the increase of the pH value in the system; i) the change of the composition of the complex, ii) the decrease of the concentration of the catalyst, iii) the decrease of the oxidation potential of the monomer.The polymerization did not proceed in either the water or the benzene solution. From this result and the solubility of the reactants, it was suggested that XOH is polymerized at the interface between water and benzene. The polymerization rate was larger in the Cu-QPVP system than in the Cu-Py system (Table 6), and then it is considered that QPVP acts as an emulsifier.

Hydrolysis of oil-soluble organic amine salts in the two-phase water-benzene system

Hydrolysis of oil-soluble organic amine salts in the two-phase water-benzene system

THE USE OF 8-HYDROXY QUINOLINE (OXINE) IN THE EXTRACTION OF SOIL ORGANIC PHOSPHORUS

A mild laboratory procedure, employing oxine in a water-benzene system, for the release of organic phosphorus from two unimproved pasture soils differing widely in total phosphorus, ratio of organic to inorganic phosphorus, pH, calcium content and clay content, is described.Data are presented showing the influence of the following factors on the amount of phosphorus released: soil to water ratio, the pH of the extraction medium, and the soil pretreatments. Under the more favourable conditions the two soils released 75 and 86 per cent of their total organic phosphorus respectively.