Use Of Binary Mixtures Research Articles

Separation of toluene from n-heptane by liquid–liquid extraction using binary mixtures of [bpy][BF4] and [4bmpy][Tf2N] ionic liquids as solvent

The use of binary mixture of ionic liquids N-butylpyridinium tetrafluoroborate ([bpy][BF4]), and 1-butyl-4-methylpyridinium bis(trifluoromethylsulfonyl)imide ([4bmpy][Tf2N]) in the liquid–liquid extraction of toluene from n-heptane has been investigated at 313.2K and atmospheric pressure. The experimental capacity of extraction and selectivity for this binary mixture has proved to be intermediate to those corresponding to the pure ionic liquids, and they can be predicted using a logarithmic–linear model of solubility. Furthermore, the results showed that the use of binary mixture of {[bpy][BF4]+[4bmpy][Tf2N]} at a mole solvent composition around 0.7 for [bpy][BF4] improves both the capacity of extraction of toluene and the selectivity with respect to those of sulfolane, the organic solvent taken as a benchmark. Thus, this mixed ionic liquid could be likely to be used in the extraction of aromatic from aliphatic in replacement to sulfolane.

Liquid–liquid extraction of toluene from n-heptane using binary mixtures of N-butylpyridinium tetrafluoroborate and N-butylpyridinium bis(trifluoromethylsulfonyl)imide ionic liquids

Liquid–liquid extraction of toluene from heptane using binary mixtures of the ionic liquids N-butylpyridinium bis(trifluoromethylsulfonyl)imide ([bpy][Tf 2N]) and N-butylpyridinium tetrafluoroborate ([bpy][BF 4]) have been investigated at 313.2 K and atmospheric pressure. On the basis of the experimental liquid–liquid equilibrium data for the pseudoternary system n-heptane + toluene + mixed ionic liquids, the values of the distribution ratio and selectivity were calculated and compared to those for the pure ionic liquids, for sulfolane, and those predicted by an ideal mixing rule. The results showed that the use of binary mixture of {[bpy][BF 4] + [bpy][Tf 2N]} at a mole solvent composition of 0.7 for [bpy][BF 4] improves both the distribution ratio of toluene and the selectivity with respect to those of sulfolane. Thus, this mixed ionic liquid could be considered an environmentally benign alternative solvent for the aromatic extraction process.

Pool boiling of perfluorocarbon mixtures on silicon surfaces

The need for higher pool boiling critical heat flux (CHF) in electronic cooling applications has turned attention to the use of binary mixtures of dielectric liquids. The available literature demonstrates that the addition of a liquid with higher saturation temperature, higher molecular weight, higher viscosity and higher surface tension can lead to significant enhancement of CHF, beyond what can be achieved through changes in pressure, liquid subcooling, and the product of surface effusivity and heater thickness. The current study focuses on extending the available data on mixture CHF enhancement, as well as pool boiling, on polished silicon surfaces to FC-72/FC-40 mixture ratios of 10%, 15%, and 20% of FC-40 by weight, a pressure range of between 1 and 3 atm, and fluid temperature from 22 to 45 °C, leading to high subcooling conditions. It is found that peak heat flux can be increased to as high as 56.8 W/cm 2 compared to 25.2 W/cm 2 for pure FC-72 at 3 atm and 22 °C. It is believed that the increase in the mixture latent heat of evaporation and surface tension, accompanying the depletion of the lower boiling point fluid in the wall region plays the major role in enhancing the critical heat flux for binary mixtures.

Molten salt synthesis of potassium and barium niobates

The interaction of powdered niobium oxide with molten potassium and barium nitrate salts containing KOH was studied. It was shown that KNbO3 can be obtained with the use of binary mixtures of the KOH-KNO3 system. The BaNb2O6 compound can be synthesized in melts of the KNO3-Ba(NO3)2 system. The treatment of Nb2O5 with melts of the system KNO3-Ba(NO3)2-KOH with various KOH percentages allowed us to obtain mixtures of Ba5Nb4O15.33 with Nb12O29 or Ba5Nb4O15.48 with K0.8Ba0.2NbO3.

New efficient reaction media for SET‐LRP produced from binary mixtures of organic solvents and H2O

AbstractSET‐LRP is mediated by a combination of solvent and ligand that promotes disproportionation of Cu(I)X into Cu(0) and Cu(II)X2. Therefore, the diversity of solvents suitable for SET‐LRP is limited. SET‐LRP of MA in a library of solvents with different equilibrium constants for disproportionation of Cu(I)X such as DMSO, DMF, DMAC, EC, PC, EtOH, MeOH, methoxyethanol, NMP, acetone and in their binary mixtures with H2O was examined. H2O exhibits the highest equilibrium constant for disproportionation of Cu(I)X. The apparent rate constant of the polymerization exhibits a linear increase with the addition of H2O. This is consistent with higher equilibrium constants for disproportionation generated by addition of H2O to organic solvents. Furthermore, with the exception of alcohols and carbonates, the rate constant of polymerization in binary mixtures could be correlated with the Dimroth‐Reichardt solvent polarity parameter. This is consistent with the single‐electron transfer mechanism proposed for SET‐LRP that involves a polar transition state. These experiments demonstrate that the use of binary mixtures of solvents with H2O provides a new, simple and efficient method for the elaboration of a large diversity of reaction media that are suitable for SET‐LRP even when one of the two solvents does not mediate disproportionation of Cu(I)X. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5577–5590, 2009

Current Developments in Heat Pipes: An Overview

Heat transfer is one of the most difficult tasks in thermal management of electronic components and directly influences cost, reliability and performances. Heat pipes are efficient heat transfer devices used in many applications, e.g. electronic systems, spacecrafts thermal control, energy collectors, power generation, chemical engineering, air conditioning, engine cooling and others. At normal operating temperatures all heat pipes have heat transfer limits imposed by the capillary transport capabilities in presence of high heat fluxes. Typical wick or capillary structures and common working fluids show advantages in some aspects and disadvantages in others. After a general introduction and a short description of the history of heat pipes developments, an overview of the current intellectual property environment and market is presented to identify trends for future developments. Then an overview of recent patents related to heat pipes technology is presented, with particular reference to: flat heat pipes, flexible heat pipes, innovative wick structures, phase change materials, innovative working fluids. Concerning flat and flexible heat pipes, a number of patents are shown that are characterized by different geometries and materials and, differently from usual cylindrical heat pipes, are particularly suited for use in microelectronics applications. Patents related to innovative wick structures are shown that are aimed to overcome some limitations associated with usual wick structures (woven mesh or sintered powder). Patented heat pipes architectures are also described that are designed to enlarge the operating temperature range by using appropriate phase change materials. In addition, recent patents are shown that exploit the use of binary mixtures as working fluids to improve the heat pipes efficiency compared to conventional pure working fluids.

Gas/liquid mass transfer in carbon dioxide–alkanes mixtures

The present paper tries to characterize the gas/liquid mass transfer processes in relation to the absorbent phase, employing binary mixtures of normal alkanes as liquid phase. The absorbent phase was in each case, had different binary relations between dodecane + heptane and dodecane + octane. Firstly, the absorption process in pure liquid phase was evaluated and characterized as regards to the operational variables. The effects produced by the mixture composition and the stirring rate upon the mass transfer process were also studied, in relation to the use of binary mixtures as liquid phases.

Micellar enhanced ultrafiltration of nitrobenzene and 4-nitrophenol

The ultrafiltration of micellar solutions containing nitrobenzene and 4-nitrophenol using three types of polymeric membranes was studied. Hexadecyltrimethylammonium bromide (CTAB), oxyethylated coconut fatty acid methyl esters of an average oxyethylation degree equal to 10 (OMC-10) and oxyethylated nonylphenol of an average oxyethylation degree equal to 9 (ONP-9) were used as surfactants. It was found that the efficiency of the separation of nitrobenzene and 4-nitrophenol could be explained using the general linear solvation energy relationships proposed by Abraham. The efficiency of separation depended upon pollutant hydrophobicity, hydrogen bond acidity, surfactant and membrane. The use of binary mixtures of cationic and nonionic surfactants enhanced the recovery. Simultaneously, a strong synergistic effect in surface activity and micellization was observed for such mixtures. The use of hydrophilic membranes seemed to be preferred due to higher fluxes and often higher retention. Ultrafiltration experiments enabled the estimation of parameters characteristic for colloids and extraction studies.

Investigation of Excipient Type and Level on Drug Release from Controlled Release Tablets Containing HPMC

The purpose of this study was to investigate the influence of excipient type and level on the release of alprazolam formulated in controlled release matrix tablets containing hydroxypropyl methylcellulose (HPMC). Each tablet formulation contained alprazolam, HPMC (Methocel K4MP), excipients, and magnesium stearate. The soluble excipients investigated were lactose monohydrate, sucrose, and dextrose, and the insoluble excipients included dicalcium phosphate dihydrate, dicalcium phosphate anhydrous, and calcium sulfate dihydrate. The similarity factor (f2 factor) was used to compare the dissolution profile of each formulation. The insoluble excipients, especially dicalcium phosphate dihydrate, caused the drug to be released at a slower rate and to a lesser extent than the soluble excipients. Soluble excipients created a more permeable hydrated gel layer for drug release, increased the porosity resulting in faster diffusion of drug, and increased the rate of tablet erosion. Use of binary mixtures of lactose monohydrate and dicalcium phosphate dihydrate produced release profiles of intermediate duration. Rapid drug dissolution was obtained when only 9.1% w/w of lactose monohydrate was present in the tablet formulation. Only when the dicalcium phosphate dihydrate level was sufficiently high (36.5% w/w) was the release rate and extent decreased. It was demonstrated that the type and level of excipient influenced the rate and extent of drug release from controlled release tablets containing HPMC. The release mechanism of alprazolam from each tablet formulation was described by either the Hixson–Crowell cube root kinetics equation or Peppas's equation. However, the different excipient types investigated did not influence the release mechanism of alprazolam from the final tablets.

Solvent engineering applied to lipase‐catalyzed glycerolysis of triolein

AbstractSolvent engineering was applied to lipase‐catalyzed glycerolysis of triolein for the selective synthesis of monoolein and diolein. The effect of different binary mixtures of n‐hexane and 2‐methyl‐2‐butanol (2M2B) on the selective production of mono‐ or diacylglyceride was established. Conditions for high selectivity toward monoolein synthesis were enhanced from 10.6 mol% in pure n‐hexane to 64 mol% in 2M2B. On the contrary, the highest production of diolein, corresponding to 62 mol%, was achieved in n‐hexane. Concerning triolein conversion, the best results were obtained in 100% 2M2B, with a conversion of 75%. The effect of the n‐hexane/2M2B ratio on diolein regioisomer production during triolein glycerolysis was also evaluated. Two different profiles of diolein regioisomers were observed as a function of solvent composition: Although the production of the 1,2‐diolein isomer was favored as the proportion of 2M2B in n‐hexane was increased, the 1,3‐isomer was preferentially synthesized in reactions where n‐hexane was the predominant solvent. When 100% n‐hexane was used as a solvent, 1,3‐diolein comprised 72 mol% of the total diolein population (58 mM). On the contrary, when the reaction was carried out in 100% 2M2B, the total concentration of diolein was lower (21 mM) but the 1,2‐diolein regioisomer was preferentially formed (89%). These results were explained as a consequence of the different extents of hydrolysis‐synthesis reactions involved in the glycerolysis process, which are strongly dependent on solvent mixtures and water concentration. Finally, some advantages of the use of binary mixtures of solvents compared with other strategies applied to glycerolysis reactions are discussed.

Electrophoretic Resolution of Tubulin and Tektin Subunits by Differential Interaction with Long-Chain Alkyl Sulfates

Tubulin dimers, formed from globular α and β subunits, and the tektins, three equimolar α-helical proteins that form filaments, mutually associate to form the junctional regions of doublet and triplet microtubules. When evaluated by SDS–PAGE, the apparent molecular weights of these proteins can deviate substantially from their sequence molecular weights in a manner sensitive to both the source of SDS and the species of origin. The electrophoretic mobility of sperm tail flagellar tubulins and tektins from an echinoderm and a mollusc were studied systematically using detergent-free stacking and resolving gels with a running buffer containing pure sodium dodecyl sulfate augmented with fixed amounts of C10, C14, C16, or C18alkyl sulfates. Although having no systematic effect on molecular weight standards, the presence of alkyl sulfates of increasing chain length progressively exaggerated the separation of tubulin subunits, similarly facilitated the separation of two normally comigrating tektins, yet minimally influenced the relative migration of adequately separated tektins. This phenomenon is most likely due to preferential binding of longer chain alkyl sulfates by specific hydrophobic regions of these otherwise similar proteins. The use of binary mixtures of pure alkyl sulfates, required in the running buffer alone, may prove useful for reproducibly separating other proteins that characteristically bind SDS anomalously.

Subcooled convective boiling of binary mixtures over an array of heated elements

Boiling data and the critical heat flux conditions are reported for both channel flow and jet impingement flow using varying concentrations of R-ll in R-113. An array of 10 flush-mounted heated elements on one wall of a vertical passage was cooled by subcooled boiling. Data indicate that for channel flow boiling, the addition of R-ll to R-113 does not produce a significant change in the critical heat flux condition. For channel flow boiling, the data indicate that addition of a small amount of a less volatile component slightly increased the critical heat flux, whereas, the addition of a small amount of a more volatile component decreased it. The critical heat flux data for channel flow were also found to agree well with critical heat flux correlations for pure fluids if the mole-weighted mean properties of the mixture were used to compute the critical heat flux from the pure fluid correlation. However, for jet impingement flow with binary mixtures, deviations existed between measured data and pure fluid correlation predictions using mole-weighted mean properties of the mixture. The significance of the findings of this study with regard to the use of binary mixtures of dielectric fluids for immersion cooling of electronic components is discussed in this article.

Raman scattering study of toluene vibrational relaxation in benzene-toluene liquid system

The polarizes and depolarized profiles of the 520 cm −1 Raman line of toluene in benzene solutions have been measured as a function of concentration. The vibrational correlation functions were obtained by Fourier inversion of Raman band contours. The concentration dependence of the experimental vibrational correlation time has been compared with that computed from the Fischer-Laubereau vibrational dephasing model modified for use in binary mixtures.

Raman study of vibrational relaxation of acetonitrile in solution

Line widths of isotropic Raman spectra of the ν1 (a1) CH or CD stretching bands of acetonitrile CH3CN and CD3CN were measured in a number of solvents. The vibrational dephasing theory, modified for use in binary mixtures, predicts quantitatively the solvent dependence of the Raman line widths.

Raman study of vibrational relaxation of benzene in solution

Measurements of the isotropic Raman spectra of the v 1(a 1g) CH stretching band of benzene in various solvents are reported. The observed band width is interpreted in terms of the vibrational dephasing model modified for use in binary mixtures.

NMR study of angular momentum relaxation in fluids. II. Mixtures of CF4 with inert gases

The effects of density and temperature on the angular momentum correlation time, τJ, in binary fluid mixtures of CF4 with Ar and Ne, respectively, are reported. The 19F spin–lattice relaxation times, T1, were measured at 56.4 MHz for 0.1, 0.25, and 0.6 mole fraction CF4 in Ar and Ne from 273 to 373 °K and pressures up to 2040 atm. The spin-rotation interactions provide the dominant relaxation mechanism for the fluorine nuclei. The experimental τJ data for CF4 infinitely dilute in Ar and Ne in the high density region (ρ≳2ρc) are successfully interpreted in terms of the rough hard sphere model (RHSM) modified for use in binary mixtures. The values of the parameter a12 characterizing the collisional efficiency of angular momentum transfer are obtained for CF4–Ar and CF4–Ne systems. The variation of τJ with mole fraction in these binary mixtures in the dense fluid region was also successfully interpreted in terms of the RHSM indicating that attractive forces are not important in determining the magnitude of the collisional efficiencies aij. At intermediate and low densities, τJ as a function of mole fraction deviates from the RHSM. As in Paper I, these deviations are interpreted in terms of the effect of attractive forces on the radial distribution function at contact.

The rate of spread of liquid pools over horizontal solid surfaces and between approaching parallel flat plates

Some measurements have been made of the rate of radial spread of liquid pools on horizontal surfaces and between approaching parallel flat plates. Graphs giving the dimensions of the pools after different intervals of time and with different surface finishes have been prepared for several liquids on different kinds of surfaces; also derived graphs relating the rate of radial flow with film thickness, etc., have been included. Movement is complex and specific to the surface and chemical character of the liquid but it is possible to follow the effect of adsorbed surface films and to correlate movement with the periphery resistance (Jamin effect). With the use of binary mixtures of liquids, correlations have been found for rate of radial spread with several properties, such as the coefficient of friction, adhesion, contact angles, and swelling. Any increase in surface activity consequent upon molecular disaggregation is accompanied by a higher rate of movement, increased adhesion, etc. Some liquids are more sensitive to the roughening of surfaces than others. The effect of viscosity usually appears to be masked by surface effects, etc., but with liquids of low Jamin resistance, apart from the initial and later stages of spreading, an approximate relation between time and the radius of the pool can be obtained both for a liquid spreading on a horizontal surface and between approaching parallel plates.