Solid + liquid equilibria of (n-alkane + cyclohexane) mixtures at high pressures

Solid+liquid equilibria (SLE) of [n-alkanes (tridecane, hexadecane, octadecane, or eicosane) + cyclohexane] at very high pressures up to about 1.0 GPa have been investigated in the temperature range from 293 to 363 K using a thermostated apparatus for the measurements of transition pressures from the liquid to the solid state in two component isothermal solutions. The freezing temperature of each mixture increases monotonously with increasing pressure. The eutectic point of the binary systems shifts to a higher temperature and to a higher n-alkane concentration with increasing pressure. The pressure–temperature–composition relation of the high-pressure solid–liquid equilibria, a polynomial based on the general solubility equation at atmospheric pressure, was satisfactorily used. Additionally, the SLE of the binary system (tridecane+cyclohexane) at normal pressure was measured by the dynamic method. The results at high pressure for all systems were compared to that at normal pressure.     

(Solid + liquid) equilibria of (nalkanes + ethyl 1,1-dimethylpropyl ether)

(Solid  +  liquid) equilibria (s.l.e.) have been measured atT >  280 K for (octadecane, or nonadecane, or eicosane, or heneicosane, or docosane, or tricosane, or tetracosane, or hexacosane, or heptacosane, or octacosane  +  ethyl 1,1-dimethylpropyl ether ETAE). The experimental results are compared with values calculated by means of the Wilson, UNIQUAC and NRTL equations utilizing parameters derived from the experimental s.l.e. The existence of a (solid  +  solid) first-order phase transition in hydrocarbons has been taken into consideration in the solubility calculations. The solubility of hydrocarbons in branched-chain ethers is lower than that in n -alkanes but higher than that in cycloalkanes, branched alkanes, 1-alcohols andtert -alcohols. The best correlation of the solubility data has been obtained by the NRTL equation where the average root-mean-square deviation of the solubility temperatures is 0.36 K.     

Solid–liquid equilibria of long chain n-alkanes (C18–C28) in N,N-dimethylacetamide

Solid–liquid equilibria (SLE) of the n-alkanes (octadecane, nonadecane, eicosane, heneicosane, docosane, tricosane, tetracosane, pentacosane, hexacosane, heptacosane and octacosane) in N,N-dimethylacetamide (DMA) are reported. The data has been measured by the dynamic method from 275 K to the melting temperatures of the n-alkane. The experimental results have been correlated by the Redlich–Kister equation with two and three parameters and the NRTL equation.     

Experimental liquid–liquid equilibria of 1-methylimidazole with hydrocarbons and ethers

The liquid–liquid equilibria (LLE) of eight binary systems containing 1-methylimidazole and n-alkanes (n-pentane, n-hexane), cyclohydrocarbons (cyclopentane, cyclohexane), aromatic hydrocarbons (hexylbenzene) or ethers (di-n-propyl ether, di-n-butyl ether, di-n-pentyl ether) have been measured from 270 K to the boiling temperature of the solvent using a “cloud point” method. Experimental solubility results are compared with values calculated by means of the NRTL equation utilizing parameters derived from LLE results.Solubility of 1-methylimidazole in many other organic solvents (aromatic hydrocarbons, branch chain ethers and ketones) has been measured at temperatures higher than 293 K and no miscibility gap was observed. The interaction of 1-methylimidazole with different solvents is discussed.     

Phase equilibrium calculations for carbon dioxide + n-alkanes binary mixtures with the Wong–Sandler mixing rules

Phase equilibrium for carbon dioxide + n-alkanes (from methane to n-decane) asymmetric binary systems was calculated using Peng–Robinson Stryjek–Vera equation of state coupled with Wong–Sandler mixing rules. NRTL model was utilized for predicting the excess Helmholtz free energy. The second virial coefficient binary interaction parameter k₁₂ and NRTL model parameters τ₁₂ and τ₂₁ for carbon dioxide + n-alkanes binary systems were optimized trough minimization of two different objective functions: one based on the calculation of the distribution coefficients, and the other one based on the determination of bubble point pressures. Generalized correlations for mixing rule parameters as a function of the n-alkane acentric factor and the equilibrium temperature were obtained from optimal parameters determined by the first objective function. Obtained results using both objective functions were satisfactory, but the estimation of the parameters calculated by the second objective function provided a better accuracy in vapor–liquid equilibrium prediction.     

Phase equilibria study of the binary systems (1-butyl-3-methylimidazolium tosylate ionic liquid + water,or organic solvent)

(Solid + liquid) phase equilibria (SLE) and (liquid + liquid) phase equilibria (LLE) for the binary systems: ionic liquid (IL) 1-butyl-3-methylimidazolim tosylate (p-toluenesulfonate) {[BMIM][TOS] + water, an alcohol (ethanol, or 1-butanol, or 1-hexanol, or 1-octanol, or 1-decanol), or n-hexane, or an aromatic hydrocarbons (benzene, or toluene, or ethylbenzene, or propylbenzene, or thiophene)} have been determined at ambient pressure. A dynamic method was used over a broad range of mole fractions and temperatures from (230 to 340) K. For the binary systems containing water, or an alcohol, simple eutectic diagrams were observed with complete miscibility in the liquid phase. As usual, with increasing chain length of the alcohol the solubility decreases. In the case of mixtures {IL + n-hexane, or benzene, or alkylbenzene, or thiophene} the eutectic systems with mutual immiscibility in the liquid phase with an upper critical solution temperature (UCST) were detected. The basic thermal properties of the pure IL, i.e. melting and glass-transition temperatures, as well as the enthalpy of fusion have been measured using a differential scanning microcalorimetry technique (DSC). Density at high temperatures was determined and extrapolated to 298.15 K. Well-known UNIQUAC, Wilson and NRTL equations have been used to correlate experimental SLE data sets for alcohols and water. For the systems containing immiscibility gaps {IL + n-hexane, or benzene, or alkylbenzene, or thiophene}, parameters of the LLE correlation equation have been derived using only the NRTL equation.     

Excess molar enthalpies of binary mixtures containing 2-decanone or dipentyl ether with long-chain n-alkanes at T = 298.15 K

Excess molar enthalpies (H^E) of binary mixtures of 2-decanone or dipentyl ether with n-alkanes, including n-dodecane, n-tetradecane, and n-hexadecane, were measured with an isothermal titration calorimeter (ITC) at T = 298.15 K under atmospheric pressure. All the measured H^E values are positive over the entire range of composition, indicating that all these mixing processes are endothermic. The H^E values varying with composition are found to be nearly symmetric for each binary system. It was also shown that the H^E values follow the order of n-hexadecane > n-tetradecane > n-dodecane at a given composition in either the 2-decanone or dipentyl ether binary systems. An empirical Redlich–Kister equation correlated quantitatively these new H^E data. The Peng–Robinson and the Patel–Teja equations of state, and the NRTL model were also applied to fit the H^E results. Among these tested correlative models, the Patel–Teja equation of state with two adjustable binary interaction parameters generally yielded the best representation.     

Solvent extraction of thiophene from n-alkanes (C7, C12, and C16) using the ionic liquid [C8mim][BF4]

In the last years, new strict environmental regulations to reduce sulfur content in liquid fuels have been established. Thiophene derivates can be considered as the key substances to be separated from liquid fuel oils. This paper reports the ability of the ionic liquid 1-methyl-3-octylimidazolium tetrafluoroborate to act as solvent in the (liquid + liquid) extraction of thiophene from aliphatic hydrocarbons. Tie-line data have been determined for ternary systems containing the ionic liquid, thiophene, and some n-alkanes at T = 298.15 K. Extraction process has been analyzed by means of thiophene distribution ratio and selectivity. The solute distribution coefficient decreases and the selectivity increases as the chain length of n-alkane increases. The use of 1-methyl-3-octylimidazolium tetrafluoroborate as potential solvent for separation of thiophene from n-alkanes is feasible using the necessary quantity of solvent. A correlation of the equilibrium data reported here has also been made, using the NRTL activity coefficient model, in order to facilitate their use in simulation and design processes.     

Liquid–liquid equilibria for n-alkanes (C12, C14, C17) + propylbenzene + NMP mixtures at temperatures between 298 and 328 K

Liquid–liquid equilibria for three ternary systems: dodecane, or tetradecane, or heptadecane + propylbenzene + NMP was studied over a temperature range of 298–328 K. The three systems studied exhibit type I liquid–liquid phase diagram. The effect of temperaure and n-alkane chain length upon solubility, selectivity, and distribution coefficient were investigated experimentally. The experimental results were regressed to estimate the interaction parameters between each of the three pairs of components for the UNIQUAC and the NRTL models as a function of temperature. Both models satisfactorily correlate the experimental data, however the UNIQUAC fit was slightly better than that obtained with the NRTL model. The values of distribution coefficient and selectivity were predicated from the equilibrium data.     

Phase equilibria study of the (N-octylisoquinolinium thiocyanate ionic liquid + aliphatic and aromatic hydrocarbon,or thiophene) binary systems

Binary liquid + liquid phase equilibria for 8 systems containing N-octylisoquinolinium thiocyanate, [C₈iQuin][SCN] and aliphatic hydrocarbon (n-hexane, n-heptane), cyclohexane, aromatic hydrocarbon (benzene, toluene, ethylbenzene, n-propylbenzene) and thiophene have been determined using dynamic method. The experiment was carried out from room temperature to the boiling-point of the solvent at atmospheric pressure. For the tested binary systems the mutual immiscibility with an upper critical solution temperature (UCST) for {IL + aliphatic hydrocarbon, or thiophene} were observed. The immiscibility gap with lower critical solution temperature (LCST) for the {IL + aromatic hydrocarbon} were determined. The parameters of the LLE correlation equation for the tested binary systems have been derived using NRTL equation. The phase equilibria diagrams presented in this paper are compared with literature data for the corresponding ionic liquids with N-alkylisoquinolinium, or N-alkylquinolinium cation and with thiocyanate – based ionic liquids. The influence of the ionic liquid structure on mutual solubility with aliphatic and aromatic hydrocarbons and thiophene is discussed.     

Ternary equilibrium data of mixtures consisting of 2-butanol,water, and heavy alcohols at T = 298.2 K

Experimental solubility curves and tie-line data for the (water + 2-butanol + organic solvents) systems were obtained at T = 298.2 K and atmospheric pressure. The organic solvents were four heavy alcohols, i.e. 1-hexanol, 1-heptanol, 1-octanol, and 1-decanol. The consistency of the experimental tie-line data was determined through the Othmer–Tobias and Bachman equations. Distribution coefficients and separation factors were calculated to evaluate the extracting capability of the solvents. The experimental data were correlated using the NRTL (α = 0.2) and UNIQUAC models, and binary interaction parameters were obtained. The average root mean square deviation values between the experimental and calculated data show the capability of these models, in particular NRTL model, in correlation of the phase behavior of the ternary systems.     

Quaternary liquid–liquid equilibria for systems of {(water + methanol or ethanol) + m-xylene + n-dodecane}

Liquid–liquid equilibrium (LLE) data were determined for the quaternary systems of {(water + methanol or ethanol) + m-xylene + n-dodecane} at three temperatures 298.15, 303.15 and 313.15 K and atmospheric pressure. The composition of liquid phases at equilibrium was determined by gas–liquid chromatography and the results were correlated with the UNIQUAC and NRTL activity coefficient models. The partition coefficients and the selectivity factor of the solvent are calculated and compared. The phase diagrams for the quaternary systems including both the experimental and correlated tie lines are presented.     

Liquid–liquid equilibrium data of water with neohexane,methylcyclohexane, tert-butyl methyl ether,n-heptane and vapor–liquid–liquid equilibrium with methane

Liquid–liquid equilibrium (LLE) data for non-aqueous liquid (neohexane [NH], tert-butyl methyl ether [TBME], methylcyclohexane [MCH], or n-heptane [nC₇]) and water have been measured under atmospheric pressure at 275.5, 283.15, and 298.15 K. It was found that TBME is the most water soluble followed by NH, MCH, and nC₇. As the temperature increased, the solubility of the non-aqueous liquids (NALs) in water decreased. The solubility of water in the non-aqueous liquid was found to increase in the following order: MCH < nC₇ < NH < TBME. It was found to increase with increasing temperature. In addition, vapour–liquid–liquid equilibrium (VLLE) data for the above binary systems with methane were measured at 275.5 K and at 120, 1000, and 2000 kPa. It was found that the vapour composition of water and NALs decreased as the pressure increased. The water content in the non-aqueous phase was not a strong function of pressure. The concentration of methane in the non-aqueous phase increased as the pressure increased. Furthermore, the concentration of the methane and NALs in the water phase increased proportionally with pressure. The solubility of methane in water followed Henry's law. It is noted that the measurements were completed prior to the onset of hydrate nucleation.     

Phase equilibrium study of the binary systems (N-hexyl-3-methylpyridinium tosylate ionic liquid + water,or organic solvent)

The (solid + liquid) phase equilibrium (SLE) and (liquid + liquid) phase equilibrium (LLE) for the binary systems ionic liquid (IL) N-hexyl-3-methylpyridinium tosylate (p-toluenesulfonate), {([HM³Py][TOS] + water, or an alcohol (1-butanol, or 1-hexanol, or 1-octanol, or 1-decanol), or an aromatic hydrocarbon (benzene, toluene, or ethylbenzene, or propylbenzene), or an alkane (n-hexane, n-heptane, n-octane)} have been determined at ambient pressure using a dynamic method. Simple eutectic systems with complete miscibility in the liquid phase were observed for the systems involving water and alcohols. The phase equilibrium diagrams of IL and aromatic or aliphatic hydrocarbons exhibit eutectic systems with immiscibility in the liquid phase with an upper critical solution temperature as for most of the ILs. The correlation of the experimental data has been carried out using the UNIQUAC, Wilson and the non-random two liquid (NRTL) correlation equations. The results reported here have been compared with analogous phase diagrams reported by our group previously for systems containing the tosylate-based ILs.     

(Liquid + liquid) equilibria in the binary systems (aliphatic,or aromatic hydrocarbons + 1-ethyl-3-methylimidazolium ethylsulfate,or 1-butyl-3-methylimidazolium methylsulfate ionic liquids)

(Liquid + liquid) equilibria of 14 binary systems composed of n-hexane, n-heptane, benzene, toluene, o-xylene, m-xylene, or p-xylene and 1-ethyl-3-methylimidazolium ethylsulfate, [emim]EtSO₄, or 1-butyl-3-methylimidazolium methylsulfate, [bmim]MeSO₄, ionic liquids have been done in the temperature range from (293.2 to 333.2) K. The solubility of aliphatic is less than those of the aromatic hydrocarbons. In particular, the solubility of hydrocarbons in both ionic liquids increases with the temperature in the order n-heptane < n-hexane < m-xylene < p-xylene < o-xylene < toluene < benzene. Considering the high solubility of aromatics and the low solubility of aliphatic hydrocarbons as well as totally immiscibility of the ionic liquids in all hydrocarbons, these new green solvents may be used as potentials extracting solvents for the separation of aromatic and aliphatic hydrocarbons.     

Isobaric vapor–liquid phase equilibria for the binary systems of tert-butanol + 2-ethyl-1-hexanol and n-butanol + 2-ethyl-1-hexanol

Isobaric vapor–liquid equilibria for the binary mixtures of tert-butanol (TBA) + 2-ethyl-1-hexanol and n-butanol (NBA) + 2-ethyl-1-hexanol were experimentally investigated at atmospheric pressure in the temperature range of 353.2–458.2 K. The raw experimental data were correlated using the UNIQUAC and NRTL models and used to estimate the interaction parameters between each pair of components in the systems. The experimental activity coefficients were obtained using the gas chromatographic method and compared with the calculated data obtained from these equilibrium models. The results show that UNIQUAC model gives better correlation than NRTL for these binary systems. The liquid–liquid extraction of TBA from aqueous solution using 2-ethyl-1-hexanol was demonstrated by simulation and the variation of separation factor of TBA at several temperatures was reported.     

(Liquid + liquid) equilibria of binary systems containing hyperbranched polymer Boltorn® H2004 – Experimental study and modelling in terms of lattice-cluster theory

(Liquid + liquid) phase equilibria (LLE) of binary mixtures containing hyperbranched polymer Boltorn® H2004 and n-alkanes (n-hexane, n-heptane, n-octane, and n-decane) were studied over the temperature range from about (260 up to 360) K. The polymer is partially miscible with n-alkanes and the solubility decreases with an increase of the chain length of the solvent. Corresponding LLE phase diagrams including spinodal and binodal (liquid + liquid) coexistence curves were calculated in terms of the statistical mechanics – based on the lattice-cluster theory, based only on the upper critical solution temperature, and the polymer chain architecture. The results show semi-qualitative agreement of predicted and experimental equilibrium compositions and temperatures. Boltorn® H2004 reveals complete miscibility in the liquid phase with alcohols (C₁–C₈), aromatic hydrocarbons (benzene, toluene, and thiophene), and ethers (methyl tetra-butyl ether, ethyl tetra-butyl ether, and tetrahydrofurane).     

Excess molar enthalpies of binary systems containing 2-octanone,hexanoic acid,or octanoic acid at T = 298.15 K

An isothermal titration calorimeter was used to measure the excess molar enthalpies (H^E) of six binary systems at T = 298.15 K under atmospheric pressure. The systems investigated include (1-hexanol + 2-octanone), (1-octanol + 2-octanone), (1-hexanol + octanoic acid), (1-hexanol + hexanoic acid), {N,N-dimethylformamide (DMF) + hexanoic acid}, and {dimethyl sulfoxide (DMSO) + hexanoic acid}. The values of excess molar enthalpies are all positive except for the DMSO- and the DMF-containing systems. In the 1-hexanol with hexanoic acid or octanoic acid systems, the maximum values of H^E are located around the mole fraction of 0.4 of 1-hexanol, but the H^E vary nearly symmetrically with composition for other four systems. In addition to the modified Redlich–Kister and the NRTL models, the Peng–Robinson (PR) and the Patel–Teja (PT) equations of state were used to correlate the excess molar enthalpy data. The modified Redlich–Kister equation correlates the H^E data to within about experimental uncertainty. The calculated results from the PR and the PT are comparable. It is indicated that the overall average absolute relative deviations (AARD) of the excess enthalpy calculations are reduced from 18.8% and 18.8% to 6.6% and 7.0%, respectively, as the second adjustable binary interaction parameter, k_bij, is added in the PR and the PT equations. Also, the NRTL model correlates the H^E data to an overall AARD of 10.8% by using two adjustable model parameters.     

Measurement and correlation of phase equilibrium data of the mixtures consisting of butyric acid,water, cyclohexanone at different temperatures

In this work, experimental solubility and tie-line data for the (water + butyric acid + cyclohexanone) system were obtained at T = (298.2, 308.2, and 318.2) K and atmospheric pressure. The ternary system investigated exhibits type-1 behavior of LLE. The experimental tie-line data were compared with those correlated by the UNIQUAC and NRTL models. The consistency of the experimental tie-line data was determined through the Othmer Tobias and Hand correlation equations. Distribution coefficients and separation factors were evaluated over the immiscibility regions. A comparison of the extracting capability of the solvent at different temperatures was made with respect to separation factors. The Katritzky and Kamlet–Abboud–Taft multiparameter scales were applied to correlate distribution coefficients and separation factors in this ternary system. The LSER models values were interpreted in terms of intermolecular interactions.     

(Solid + liquid) phase equilibria of binary mixtures containing N-methyl-2-pyrrolidinone and ethers at atmospheric pressure

Solid–liquid equilibria (SLE), have been measured from 270 K to the boiling temperature of the solvent for 10 binary mixtures of N-methyl-2-pyrrolidinone, with ethers (dipropyl ether, dibutyl ether, dipentyl ether, methyl 1,1-dimethylethyl ether, methyl 1,1-dimethylpropyl ether, ethyl 1,1-dimethylpropyl ether, 1,4-dioxane, tetrahydrofuran, tetrahydropyran, 18-crown-6) using a dynamic method. The solubility of N-methyl-2-pyrrolidinone in ethers is lower than in alcohols and generally decreases with an increase of the number of carbon atoms of ether chain. The highest intermolecular solute–solvent interaction is observed for the cyclic ethers and for methyl 1,1-dimethylethyl ether.Experimental solubility results are compared with values calculated by means of the Wilson, UNIQUAC ASM and two NRTL equations utilizing parameters derived from SLE results. The existence of a solid–solid first-order phase transition in 18-crown-6 ether has been taken into consideration in the calculations. The correlation of the solubility data has been obtained with the average root-mean-square deviation of temperature σ_T = 0.9 K with UNIQUAC ASM and two NRTL equations and 0.6 K with the Wilson equation.