Prediction of heats of mixing of liquid mixtures containing aliphatic hydrocarbons and ketones by a group solution model

A group solution model for heats of mixing of liquid mixtures has been tested and found satisfactory for mixtures containing ketones and alkanes. No provision was made for a skeletal contribution Group contribution functions were generated from experimental data on acetone/n-hexane mixtures at 25°C and are presented. These functions allow the prediction of heats of mixing of binary or multicomponent mixtures containing alkanes and/or ketones at 25°C. No experimental data are required     

Intermolecular interactions between bovine serum albumin and certain water‐soluble polymers at various temperatures

Viscometric behaviors of dextran (Dx), poly(N‐vinyl‐2‐pyrrolidone) (PVP), and poly(ethylene oxide) (PEO) with bovine serum albumin (BSA) in aqueous solutions have been studied at 25, 30, and 35°C. The reduced viscosity and intrinsic viscosity have been experimentally measured for the polymer/water and polymer/BSA/water systems by classical Huggins equation. Measurements of reduced viscosities of the Dx, PVP, and PEO in water have been calculated and all intrinsic viscosities of PEO([η]_PEO) are larger than that of Dx([η]_Dx), and PVP([η]_PVP) in aqueous solutions, at all temperatures. The intrinsic viscosities of PVP, PEO, and Dx were found to be dependent on the concentration of BSA. The presence of BSA (0.05, 0.10, and 0.30 wt %) led to a decrease in the intrinsic viscosities of polymers, at 25, 30, and 35°C. The concentration difference of BSA (Δ[BSA]) is most effective in decreasing the intrinsic viscosities of Dx at 25°C and PEO at 30 and 35°C. In other words, Δ[η] (%) order followed as Dx > PEO > PVP at 25°C and PEO > Dx > PVP at 30 and 35°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1554–1560, 2006     

Studies on ion—solvent interactions through viscosity measurements—potassium iodide in N,N-dimethylformamide—water mixtures

The viscosities of DMF—water mixtures and of KI solutions in these mixed solvents have been measured at 25°, 30°, 35° and 40° C, covering the whole range of solvent composition. The Jones—Dole B-Coefficient, after passing through a minimum in water-rich solvent composition region, increases with the increase in DMF content in the solvent mixture. The variation of viscosity of the solvent mixture and of B-coefficient with solvent composition and temperature have been discussed in terms of solvent—solvent and ion—solvent interactions.     

Rheology of vegetable oil analogs and triglycerides

The rheological properties of two complex mixtures of short-chain triglycerides were experimentally determined. Dynamic or absolute viscosities of the mixtures were measured for shear rates of 0.32 to 64.69 s⁻¹ at temperatures between 25 and 80°C. The compositions of the mixtures were based on the oil of the plant species Cuphea viscosissima VS-320, a natural source of short-chain triglycerides. The dynamic viscosities of these mixtures were compared to those of a traditional vegetable oil (peanut oil) and diesel fuel. The results of this comparison were used to make estimates of the performance of such triglyceride mixtures as diesel fuel substitutes, since viscosity can be a key indicator of fuel performance for possible substitute diesel fuels. The crystallization temperatures of these two mixtures were also determined experimentally, and the effects of crystallization on fuel performance were projected. Additionally, the dynamic viscosities of pure triglycerides from C6∶0 to C18∶0 at 75°C were plotted vs. chain length. These viscosities were measured at high shear rates (>6 s⁻¹) where dynamic viscosity is shear-independent. An obvious trend in the relationship between triglyceride chain length and viscosity was observed. A second-order regression was used to obtain an equation for this relationship. This equation was used as a model for composition dependence of viscosity. This model was applied to the viscosities of the triglyceride mixtures examined here. There was good agreement between the model and the actual, measured viscosity values determined in this study.     

Prediction of thermodynamic properties of polar mixtures by a group solution model

A modified group solution model for liquid mixtures is presented. The model differs from previous models in that the Bronsted-Koefoed congruence principle is used to describe the effect of molecular size. The model has been tested for mixtures involving paraffin hydrocarbons, alcohols and water at low pressures. Such systems involve binary mixtures of the groups methylene and hydroxyl, and are reasonably represented by the model. Data presented enable the approximate equilibrium properties of such solutions at low pressures to be predicted at 40°C and 90°C. Interpolation and reasonable extrapolation from these temperatures should be satisfactory.     

Prediction of heats of mixing by a group solution model with application to alkane/alcohol mixtures

Group solution models of liquid mixtures have been used previously to predict excess free energies of non-ideal systems. With increasing experimental data available on heats of mixing, the application of a similar model to excess enthalpies has been investigated. The model allows for both structural and group contributions to excess enthalpies. The former contribution is determined from experimental data on mixtures of alkanes. The group contribution has been determined at 25°C and 45°C for systems containing alkanes and alcohols. Predictions require no experimental data on the system in question, and are in good agreement with experiment. Limited extrapolation to other temperatures and group compositions should be satisfactory.     

Prediction of excess free energies by a group solution model with application to alkane/ketone mixtures

The group solution model of Ratcliff and Chao for the excess free energies of liquid mixtures has been tested and found satisfactory for eight mixtures of alkanes and ketones. The model was tested by comparing experimental and predicted vapor-liquid equilibrium data. Group contribution functions were generated from experimental data on acetone/n-heptane mixtures at 65°C, and are presented. These functions allow the prediction of excess free energies of binary or multicomponent mixtures containing alkanes and ketones at 65°C. No experimental data is required. Predictions at temperatures close to 65°C, using the same functions, should be satisfactory.     

Liquid-liquid equilibria of (MTBE or TAME) + ethanol + water mixtures

Experimental liquid-liquid equilibrium data obtained at 25 and 35°C for ternary mixtures of MTBE + ethanol + water, and at 25, 35 and 45°C for ternary mixtures of TAME + ethanol + water, were satisfactorily fitted with NRTL and UNI-QUAC equations using the correlation program developed by Sørensen (1980).     

Prediction of excess free energies of liquid mixtures containing aromatic hydrocarbons using a group solution model

The group solution model of Ratcliff and Chao for the excess free energies of liquid mixtures has been tested and found satisfactory for six mixtures of alcohols and aromatic hydrocarbons. The model was tested by comparing experimental and predicted vapor-liquid equilibrium data. The assumption that aliphatic and aromatic carbon atoms are equivalent appears satisfactory for the mixtures considered. Group contribution functions were generated from experimental data on ethanol/benzene mixtures at 45°C, and are presented. These functions allow the prediction of excess free energies of mixtures containing alcohols and aromatic hydrocarbons at 45°C. No experimental data is required. Predictions at temperatures close to 45°C, using the same functions, should be satisfactory. The group contribution functions were close to those generated previously from alcohol/alkane data. The latter may be used for predicting excess free energies of alcohol/aromatic hydrocarbon mixtures with little loss of accuracy.     

Rheological Characterization of Anaerobic Sludge from Agricultural and Bio‐Waste Biogas Plants

Anaerobic sludges taken from 16 different biogas plants were analyzed with respect to their rheological characteristics. All sludges showed temperature‐dependent shear‐thinning behavior with viscosities from 900 – 6000 mPa s at 20 °C. Nevertheless, the liquid fraction of the anaerobic sludges also revealed temperature‐dependent, shear‐thinning behavior with viscosities well above water viscosity (2 – 40 mPa s at 20 °C). The rheological behavior of the liquid phase could be linked to organic fractions, i.e., proteins and polysaccharides. Shear‐thinning and temperature‐dependent behavior was modeled by the power‐law equation and the Arrhenius law, respectively.     

Prediction of heats of mixing of liquid mixtures by an analytical group solution model

An analytical group solution model has been developed for the prediction of heats of mixing of liquid mixtures using the Wilson equation. This procedure obviates some of the limitations and inaccuracies of the previous model, and is well suited to computer calculation. It was tested for a wide range of alcohol/alkane mixtures and gives good results. The group Wilson parameters were generated from experimental data for methylene/hydroxyl mixtures at 15°C to 55°C. At temperatures within or close to this range, these group parameters allow prediction of heats of mixing of binary or multicomponent mixtures containing these two groups. No experimental data are required.     

Effect of hydrogenation on density and viscosity of sunflowerseed oil

The densities and viscosities of unhydrogenated and hydrogenated sunflowerseed oils have been determined at temperatures ranging from 25 to 50°C at 5°C intervals. The densities of these oils vary linearly with temperature. The values of the parameters for the density equation have been calculated. Smooth curves were obtained when the changes in viscosity with temperature were plotted in the form of ln η vs. 1/T. The energy of activation, the free energy of activation, and the entropy of activation have been calculated at 25°C, and they decreased with the degree of unsaturation in the fatty acid chains of the sunflowerseed oil.     

Measurement of vapor-liquid equilibria using a semi-continuous total pressure static equilibrium still

The total pressure static equilibrium still designed by Gibbs and Van Ness has been modified to increase its accuracy. It was tested by comparing calculated vapor compositions and excess Gibbs free energies with literature data for mixtures of ethanol and n-heptane at 30°C. Experimental data are presented for 1-pentanol/n-hexane mixtures at 30° and 50°C, for 1-pentanol/n-pentane mixtures at 30°C, and for 1-butanol/n-pentane mixtures at 30°C.     

Prediction of heats of mixing of liquid mixtures containing alkane,chloroalkane and alcohol by an analytical group solution model

An analytical group solution model (AGSM) previously developed for the prediction of heats of mixing has been applied to ternary group, ternary component mixtures. A simple temperature dependence is proposed for the group interaction parameters. Temperature independent coefficients were obtained in the temperature range 15 to 35°C for mixtures containing CH₂, OH and Cl groups. These coefficients allow the prediction of heat of mixing for binary or ternary mixtures containing alcohols, chloroalkanes and alkanes. Heats of mixing for the following systems are reported: 1-chlorobutane and 2-chlorobutane with both n-hexane and n-octanol at 35°C; n-octanol — n-hexane at 25 and 35°C; and three chords of the ternary system 1-chlorobutane — n-octanol — n-hexane at 25 and 35°C.     

Separation of gas and organic/water mixtures by MFI type zeolite membranes synthesized in a flow system

MFI type zeolite membranes were synthesized in a recirculating flow system at 95 °C where the synthesis solution was flown over the tubular α-alumina supports. The performance of the membranes for the separation of binary gas mixtures and alcohol/water liquid mixtures was investigated. A membrane synthesized by two consecutive synthesis steps had a separation selectivity of 15 and 11 for equimolar mixtures of n-C₄H₁₀/CH₄ and n-C₄H₁₀/N₂ at 200 °C, respectively. The membrane selectively permeated large n-C₄H₁₀ over small CH₄ and N₂, suggesting that the separation is essentially adsorption-based and the membrane has few nonselective intercrystalline pores. The selectivities in the pervaporation separation of 5% ethanol/95% water mixture were 43 and 23 with permeate fluxes of 0.2 and 1.9 kg/m² h at 25 and 85 °C, respectively. The separation performance of membranes showed that MFI type membranes prepared in a recirculating flow system can be used both in the separation of gas and liquid mixtures.     

Synthesis and characterization of cholesteric thermotropic liquid crystalline polyesters

Cholesteric liquid crystalline polyesters were successfully synthesized from isosorbide, methyl hydroquinone, and isophthaloyl chloride. Homo/copolyesters were synthesized by the solution polycondensation method, for which a mild organic base such as pyridine was employed. Inherent viscosities of polyesters P‐3–P‐5 were in the range of 0.31–0.39 dL/g at 25°C in chloroform, and polyesters P‐1 and P‐2 were insoluble in chloroform. Homo/copolyesters based on isosorbide, methyl hydroquinone, and isophthalic acid had thermal stability at more than 300°C on the basis of 10% weight loss. The thermotropic liquid crystalline properties were examined by differential scanning calorimetry and polarizing optical microscopy. Wide‐angle X‐ray diffraction study demonstrated that polyesters P‐1, P‐2, and P‐3 were semicrystalline, whereas the degree of crystallinity of polyesters P‐4 and P‐5 was less than 5%. Copolyester P‐4 showed formation of a yellow iridescent streak at 209°C on heating and development of a Grandjean texture at 270°C on heating. These are typical textures of the cholesteric liquid crystalline phase. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1232–1237, 2007     

Determination of the molecular weight and hydrodynamic dimensions of micelles formed from a block copolymer

An investigation has been made of micelle formation by a polystyrene-polyisoprene two-block copolymer in n-decane. For the sample studied the number-average molecular weights of the polystyrene block and overall copolymer chain were 13 000 and 51 000 respectively. Light-scattering studies in n-decane were made within the temperature range 25–65°C. Conventional light scattering was used to obtain weight-average molecular weights; at 25°C, M_w of the micelles was 1·73±0·14×10⁶. Translational diffusion coefficients were determined from Rayleigh linewidth measurements; the micelles were found to have a hydrodynamic radius of 19·6nm at 25°C. Intrinsic viscosities were determined for the copolymer in n-decane and methyl cyclohexane within the temperature range ?20° to 75°C. Finally, data obtained earlier in an electron microscopy study of freezeetched specimens were compared with the results obtained in the present study.     

A resolution with the congruence principle of viscosity in mixtures of n-hexadecane and l-n-chloroalkanes at 25°C

The viscosity of binary mixtures of n-hexadecane with nine normal 1-chloroalkanes from butyl through octadecyl at 25°C. is considered. This includes a range in kinematic viscosities from less than 0.5 to more than 8.5 centistokes. Resolution of departures from ideal flow, as defined with the Eyring viscosity equation, into homogeneous and heterogeneous aspects is described in terms of the restricted principle of congruence. Experimental viscosity values agree within about 1% with those calculated through the relationships obtained by the resolution. The method is also considered for the estimation of viscosities of mixtures of the present systems.     

Condensation polymerization of pyrogallol and benzaldehyde

Novolac-type polycondensation of benzaldehyde (B) and pyrogallol (P) has been carried out at 60°C, 75°C and 90°C and at B/P mole ratios of 1.5 and 3.0 using phosphoric acid as catalyst. The reaction follows a 2nd order rate law. By using GC consumption data of benzaldehyde and pyrogallol, kinetic parameters such as the overall rate constants, activation energies (E_a) and logA values are investigated. The activation energies for 1.5 and 3.0 B/P mole ratios are found as 62.3 kJ mol^?1 and 56.4 kJ mol^?1, respectively. The molecular weights of the resins determined by measuring intrinsic viscosities (25°C, THF) are in the range of 0.03 to 0.07 dL g^?1 at various temperatures and B/P mole ratios.     

Viscosity studies of some polyamides dissolved in mixed solvents (cosolvents)

The solubility of poly (octamethylene sebacamide) (POS), poly (octamethylene terephthalamide) (POT) and poly (octamethylene tetrachloroterephthalamide) (POTC1), in $\text{m-}\text{cresol}\text{cyclohexane}$ mixtures, a cosolvent system, has been studied by measuring the intrinsic viscosity [η], at 25°C. The intrinsic viscosities of POT, POS and POTC1 in various solvent/non-solvent mixtures are higher than the corresponding intrinsic viscosities in the pure solvent m-cresol. The POT and POTC1 polyamides exhibit a sharp increase in [η] values compared with the corresponding small increase in the POS polyamide. The POTC1 polyamide presents a true cosolvency effect in $\text{m-}\text{cresol}\text{cyclohexane}$ mixtures; m-cresol and cyclohexane are non-solvents for this polyamide. The cosolvent behaviour is discussed in terms of the most energetically favourable interactions. The aromatic ring in POT and POTC1 would expand the chain, would favour a better packing between neighbouring solvent molecules and would favour the selective adsorption in the cosolvent system.