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Papers by Luis Sanz

The Journal of Chemical Thermodynamics, 2019

The liquid-liquid equilibrium (LLE) curves have been determined for the 2-hydroxyl-benzaldehyde (... more The liquid-liquid equilibrium (LLE) curves have been determined for the 2-hydroxyl-benzaldehyde (salicylaldehyde, SAC) + CH 3 (CH 2) n CH 3 mixtures (n = 5,6,7,8,9). The equilibrium temperatures were determined observing, by means of a laser scattering technique, the turbidity produced on cooling when a second phase takes place. All the systems show an upper critical solution temperature, which linearly increases with n. Intermolecular effects have been investigated in alkanol + benzaldehyde systems using data from the literature. Interactions in 1-alkanol mixtures are mainly of dipolar type. The corresponding excess molar enthalpies, H E m , are large and positive, which reveals that interactions between like molecules are dominant. Interactions between unlike molecules are stronger for the methanol-containing system. For the other mixtures, the enthalpy of the 1-alkanol-benzaldehyde interactions remains more or less constant. At 298.15 K and equimolar composition, the replacement of a linear polar solvent by the isomeric aromatic one leads to increased H E m values in systems with a given 1-alkanol. The phenol + benzaldehyde system shows strongly negative deviations from the Raoult's law. Proximity effects have been examined in SAC + hydrocarbon mixtures. Alkane-containing systems are essentially characterized by dipolar interactions, while dispersive interactions are prevalent in the solution with benzene. All the mixtures have been treated in terms of DISQUAC. The interaction parameters for the OH/CHO contacts and for the SAC/aromatic and SAC/alkane contacts have been reported. DISQUAC provides a correct description of the thermodynamic properties considered. In the case of SAC systems, this is done by defining a new specific group HO-CC -CHO for salicylaldehyde.

Journal of Molecular Liquids, 2018

Liquid-liquid equilibria for the systems 2-ethoxybenzenamine + CH3(CH2)nCH3 (n = 6,8,10,12) and 4... more Liquid-liquid equilibria for the systems 2-ethoxybenzenamine + CH3(CH2)nCH3 (n = 6,8,10,12) and 4-ethoxybenzenamine + CH3(CH2)nCH3 (n = 5,6

Journal of Chemical & Engineering Data, 2018

The liquid−liquid equilibrium (LLE) curves for 2-phenylethan-1-ol (2-phenylethanol, 2PhEtOH) + oc... more The liquid−liquid equilibrium (LLE) curves for 2-phenylethan-1-ol (2-phenylethanol, 2PhEtOH) + octane, + decane, + dodecane, + tetradecane or + 2,2,4-trimethylpentane have been determined by a method of turbidimetry using a laser scattering technique. Experimental results reveal that the systems are characterized by an upper critical solution temperature (UCST), which increases linearly with the number of C atoms of the n-alkane. In addition, the LLE curves have a rather horizontal top and become skewed to higher mole fractions of the n-alkane, when its size increases. For a given n-alkane, UCST decreases as follows: phenol > phenylmethanol > 2-PhEtOH, indicating that dipolar interactions decrease in the same sequence. This has been ascribed to a weakening in the same order of the proximity effects between the phenyl and OH groups of the aromatic alkanols. DISQUAC interaction parameters for OH/aliphatic and OH/aromatic contacts in the investigated systems are reported. Phenol, or phenylmethanol or 2-PhEtOH, + n-alkane mixtures only differ by the first dispersive Gibbs energy interaction parameter for the (OH/aliphatic) contact. 52 2.1. Materials. Information on source, purity, water 53 contents, determined by the Karl Fischer method, and density 54 (ρ) of the pure chemicals employed along this investigation is 55 t1 collected in Table 1. All the chemicals were used as received. 56 Density values were obtained from a vibrating-tube densimeter 57 and a sound analyzer, Anton Paar model DSA-5000. The 58 repeatability of the ρ measurements is 5 × 10 −3 kg•m −3 , while 59 their relative standard uncertainty is 0.001. Inspection of Table 60 1 shows that there is a good agreement between our density 61 results and those taken from the literature. 62 2.2. Apparatus and Procedure. Mixtures were prepared 63 by mass in small Pyrex tubes of the following dimensions: 0.009 64 m i.d. and about 0.04 m length (free volume of the ampule 65 ≈1.17 × 10 −6 m 3). The tubes were immediately sealed by 66 capping at 0.1 MPa and 298.15 K. Weights were measured 67 using an analytical balance Sartorius NSU125p (weighing 68 accuracy 10 −8 kg). Mole fractions were calculated on the basis 69 of the relative atomic mass Table of 2015 issued by the

The Journal of Chemical Thermodynamics, 2015

∆ for (methanol + cylohexylamine) at (293.15-303.15) K are reported. • Large negative E m V value... more ∆ for (methanol + cylohexylamine) at (293.15-303.15) K are reported. • Large negative E m V values and positive η ∆ values reveal the existence of strong methanol-amine interactions • Alcohol-cyclohexylamine interactions become weaker when the size of the alcohol increases • Positive E r ε values indicate that dielectric polarization is strengthened along the mixing process The experimental data have been also used to calculate K g , m P , and the corresponding excess magnitudes.

Journal of Chemical & Engineering Data, 2012

The liquid-liquid equilibrium (LLE) curves for (phenylmethanol + CH 3 (CH 2) n CH 3) mixtures (n ... more The liquid-liquid equilibrium (LLE) curves for (phenylmethanol + CH 3 (CH 2) n CH 3) mixtures (n = 5,6,8,10,12) have been obtained by the critical opalescence method using a laser scattering technique. All the systems show an upper critical solution temperature (UCST). In addition, the LLE curves have a rather horizontal top and their symmetry depends on the alkane size. The UCST increases almost linearly with n. For systems including a given alkane and phenol or phenylmethanol, the UCST is much higher than that of the corresponding mixtures with hexan-1-ol or heptan-1-ol. This reveals that dipolar interactions are stronger in solutions with aromatic alcohols. Preliminary DISQUAC interaction parameters for OH/aliphatic contacts in the investigated systems were obtained. It is remarkable that the coordinates of the critical points of (phenol or phenylmethanol + alkane) mixtures can be described using the same quasichemical interaction parameters for the OH/aliphatic and OH/aromatic contacts.

Industrial & Engineering Chemistry Research, 2013

1-Alkanol + alkanone systems have been investigated through the data analysis of molar excess fun... more 1-Alkanol + alkanone systems have been investigated through the data analysis of molar excess functions, enthalpies, isobaric heat capacities, volumes and entropies, and using the Flory model and the formalism of the concentration-concentration structure factor (CC (0) S). The enthalpy of the hydroxyl-carbonyl interactions has been evaluated. These interactions are stronger in mixtures with shorter alcohols (methanol-1-butanol) and 2-propanone, or 2butanone. However, effects related to the self-association of alcohols and to solvation between unlike molecules are of minor importance when are compared with those which arise from dipolar interactions. Physical interactions are more relevant in mixtures with longer 1-alkanols. The studied systems are characterized by large structural effects. The variation of the molar excess enthalpy with the alcohol size along systems with a given ketone, or with the alkanone size in solutions with a given alcohol are discussed in terms of the different contributions to this excess function. Mixtures with methanol show rather large orientational effects. The random mixing hypothesis is attained in large extent for mixtures with 1-alkanols ≠ methanol and 2alkanones. Steric effects and cyclization lead to stronger orientational effects in mixtures with 3pentanone, 4-heptanone or cyclohexanone. The increase of temperature weakens orientational effects. Results from CC (0) S calculations show that homocoordination is predominant and support conclusions obtained from the Flory model,

Fluid Phase Equilibria, 2007

The binodal curves of the liquid–liquid equilibria (LLE) for systems of o-toluidine with heptane,... more The binodal curves of the liquid–liquid equilibria (LLE) for systems of o-toluidine with heptane, octane, nonane, decane or dodecane have been determined visually. All the curves show an upper critical solution temperature (UCST), which increases with the chain length of the alkane. The bimodal curves have a rather flat horizontal top and their symmetry depends on the chain length of

Journal of Solution Chemistry, 2020

Densities, , and kinematic viscosities, , have been determined at atmospheric pressure and at 293... more Densities, , and kinematic viscosities, , have been determined at atmospheric pressure and at 293.15-303.15 K for binary mixtures formed by methanol and one linear polyether of the type CH 3-O-(CH 2 CH 2 O) n-CH 3 (n = 2, 3, 4). Measurements on and were carried out, respectively, using an Anton Paar DMA 602 vibrating-tube densimeter and an Ubbelohde viscosimeter. The values were used to compute excess molar volumes, V E m , and, together with the results, dynamic viscosities (). Deviations from linear dependence on mole fraction for viscosity, Δ , are also provided. Different semi-empirical equations have been employed to correlate viscosity data. Particularly, the equations used are the: Grunberg-Nissan, Hind, Frenkel, Katti-Chaudhri, McAllister and Heric. Calculations show that better results are obtained from the Hind equation. The V E m values are large and negative and contrast with the positive excess molar enthalpies, H E m , available in the literature, for these systems. This indicates that structural effects are dominant. The Δ results are positive and correlate well with the difference in volumes of the mixture compounds, confirming the importance of structural effects. The temperature dependences of and of the molar volume have been used to calculate enthalpies, entropies and Gibbs energies, ΔG * , of viscous flow. It is demonstrated that ΔG * is essentially determined by enthalpic effects. Methanol + CH 3-O-(CH 2 CH 2 O) n-CH 3 mixtures have been treated in the framework of the ERAS model. Results for H E m are acceptable, while the composition dependence of the V E m curves is poorly represented. This has been ascribed to the existence of strong dipolar and structural effects in the present solutions.

The Journal of Chemical Thermodynamics, 2015

Abstract Densities, ρ , kinetic viscosities, ν , and refractive indices, n D , have been measured... more Abstract Densities, ρ , kinetic viscosities, ν , and refractive indices, n D , have been measured for (1-heptanol or 1-decanol + cyclohexylamine) systems at T = (293.15 to 303.15) K. The experimental ρ , ν , n D values were obtained using an Anton Paar DMA 602 vibrating-tube densimeter, an Ubbelohde viscosimeter and a refractometer model RMF970, respectively. These data are used to determine a number of derived properties: excess molar volumes, V m E , dynamic viscosities, η , deviations of this magnitude from linear dependence on mole fraction, Δ η , Gibbs energies of activation of viscous flow, Δ G ∗ , deviations of n D from the ideal state, Δ n D , or molar refractions, R m . In addition, (1-alkanol + cyclohexylamine) mixtures have been studied by means of the ERAS model. The corresponding parameters are reported. Viscosity data have been correlated by the following semi-empirical equations: Grunberg–Nissan, Hind, Frenkel, Katti–Chaudhri, Tamura–Kurata, Teja–Rice, McAllister and Heric. The deviations obtained are usually lower than 2%. The large negative V m E values of the studied solutions reveal the existence of strong alcohol-amine interactions. The properties V m E and R m increase with the increasing of the chain length of the 1-alcohol, while Δ η and Δ n D decrease. These variations suggest that interactions between unlike molecules are weakened and dispersive interactions become more important when the alcohol size increases. On the other hand, Δ G ∗ is essentially determined by enthalpic effects. The effect of replacing cyclohexylamine by an isomeric amine, hexylamine (HxA), dipropylamine (DPA) or N,N,N-triethylamine (TEA) in mixtures with a given 1-alkanol is also investigated. It is shown that the strength of the methanol-amine interactions become stronger in the sequence: TEA ≈ cyclohexylamine. The application of the ERAS model to (1-alcohol + cyclohexylamine) mixtures supports these findings. The parameters obtained in this work fit well into the general ERAS treatment of (1-alkanol + amine) systems.

Fluid Phase Equilibria, 2007

The Journal of Chemical Thermodynamics, 2019

The liquid-liquid equilibrium (LLE) curves have been determined for the 2-hydroxyl-benzaldehyde (... more The liquid-liquid equilibrium (LLE) curves have been determined for the 2-hydroxyl-benzaldehyde (salicylaldehyde, SAC) + CH 3 (CH 2) n CH 3 mixtures (n = 5,6,7,8,9). The equilibrium temperatures were determined observing, by means of a laser scattering technique, the turbidity produced on cooling when a second phase takes place. All the systems show an upper critical solution temperature, which linearly increases with n. Intermolecular effects have been investigated in alkanol + benzaldehyde systems using data from the literature. Interactions in 1-alkanol mixtures are mainly of dipolar type. The corresponding excess molar enthalpies, H E m , are large and positive, which reveals that interactions between like molecules are dominant. Interactions between unlike molecules are stronger for the methanol-containing system. For the other mixtures, the enthalpy of the 1-alkanol-benzaldehyde interactions remains more or less constant. At 298.15 K and equimolar composition, the replacement of a linear polar solvent by the isomeric aromatic one leads to increased H E m values in systems with a given 1-alkanol. The phenol + benzaldehyde system shows strongly negative deviations from the Raoult's law. Proximity effects have been examined in SAC + hydrocarbon mixtures. Alkane-containing systems are essentially characterized by dipolar interactions, while dispersive interactions are prevalent in the solution with benzene. All the mixtures have been treated in terms of DISQUAC. The interaction parameters for the OH/CHO contacts and for the SAC/aromatic and SAC/alkane contacts have been reported. DISQUAC provides a correct description of the thermodynamic properties considered. In the case of SAC systems, this is done by defining a new specific group HO-CC -CHO for salicylaldehyde.

Journal of Molecular Liquids, 2018

Liquid-liquid equilibria for the systems 2-ethoxybenzenamine + CH3(CH2)nCH3 (n = 6,8,10,12) and 4... more Liquid-liquid equilibria for the systems 2-ethoxybenzenamine + CH3(CH2)nCH3 (n = 6,8,10,12) and 4-ethoxybenzenamine + CH3(CH2)nCH3 (n = 5,6

Journal of Chemical & Engineering Data, 2018

The liquid−liquid equilibrium (LLE) curves for 2-phenylethan-1-ol (2-phenylethanol, 2PhEtOH) + oc... more The liquid−liquid equilibrium (LLE) curves for 2-phenylethan-1-ol (2-phenylethanol, 2PhEtOH) + octane, + decane, + dodecane, + tetradecane or + 2,2,4-trimethylpentane have been determined by a method of turbidimetry using a laser scattering technique. Experimental results reveal that the systems are characterized by an upper critical solution temperature (UCST), which increases linearly with the number of C atoms of the n-alkane. In addition, the LLE curves have a rather horizontal top and become skewed to higher mole fractions of the n-alkane, when its size increases. For a given n-alkane, UCST decreases as follows: phenol > phenylmethanol > 2-PhEtOH, indicating that dipolar interactions decrease in the same sequence. This has been ascribed to a weakening in the same order of the proximity effects between the phenyl and OH groups of the aromatic alkanols. DISQUAC interaction parameters for OH/aliphatic and OH/aromatic contacts in the investigated systems are reported. Phenol, or phenylmethanol or 2-PhEtOH, + n-alkane mixtures only differ by the first dispersive Gibbs energy interaction parameter for the (OH/aliphatic) contact. 52 2.1. Materials. Information on source, purity, water 53 contents, determined by the Karl Fischer method, and density 54 (ρ) of the pure chemicals employed along this investigation is 55 t1 collected in Table 1. All the chemicals were used as received. 56 Density values were obtained from a vibrating-tube densimeter 57 and a sound analyzer, Anton Paar model DSA-5000. The 58 repeatability of the ρ measurements is 5 × 10 −3 kg•m −3 , while 59 their relative standard uncertainty is 0.001. Inspection of Table 60 1 shows that there is a good agreement between our density 61 results and those taken from the literature. 62 2.2. Apparatus and Procedure. Mixtures were prepared 63 by mass in small Pyrex tubes of the following dimensions: 0.009 64 m i.d. and about 0.04 m length (free volume of the ampule 65 ≈1.17 × 10 −6 m 3). The tubes were immediately sealed by 66 capping at 0.1 MPa and 298.15 K. Weights were measured 67 using an analytical balance Sartorius NSU125p (weighing 68 accuracy 10 −8 kg). Mole fractions were calculated on the basis 69 of the relative atomic mass Table of 2015 issued by the

The Journal of Chemical Thermodynamics, 2015

∆ for (methanol + cylohexylamine) at (293.15-303.15) K are reported. • Large negative E m V value... more ∆ for (methanol + cylohexylamine) at (293.15-303.15) K are reported. • Large negative E m V values and positive η ∆ values reveal the existence of strong methanol-amine interactions • Alcohol-cyclohexylamine interactions become weaker when the size of the alcohol increases • Positive E r ε values indicate that dielectric polarization is strengthened along the mixing process The experimental data have been also used to calculate K g , m P , and the corresponding excess magnitudes.

Journal of Chemical & Engineering Data, 2012

The liquid-liquid equilibrium (LLE) curves for (phenylmethanol + CH 3 (CH 2) n CH 3) mixtures (n ... more The liquid-liquid equilibrium (LLE) curves for (phenylmethanol + CH 3 (CH 2) n CH 3) mixtures (n = 5,6,8,10,12) have been obtained by the critical opalescence method using a laser scattering technique. All the systems show an upper critical solution temperature (UCST). In addition, the LLE curves have a rather horizontal top and their symmetry depends on the alkane size. The UCST increases almost linearly with n. For systems including a given alkane and phenol or phenylmethanol, the UCST is much higher than that of the corresponding mixtures with hexan-1-ol or heptan-1-ol. This reveals that dipolar interactions are stronger in solutions with aromatic alcohols. Preliminary DISQUAC interaction parameters for OH/aliphatic contacts in the investigated systems were obtained. It is remarkable that the coordinates of the critical points of (phenol or phenylmethanol + alkane) mixtures can be described using the same quasichemical interaction parameters for the OH/aliphatic and OH/aromatic contacts.

Industrial & Engineering Chemistry Research, 2013

1-Alkanol + alkanone systems have been investigated through the data analysis of molar excess fun... more 1-Alkanol + alkanone systems have been investigated through the data analysis of molar excess functions, enthalpies, isobaric heat capacities, volumes and entropies, and using the Flory model and the formalism of the concentration-concentration structure factor (CC (0) S). The enthalpy of the hydroxyl-carbonyl interactions has been evaluated. These interactions are stronger in mixtures with shorter alcohols (methanol-1-butanol) and 2-propanone, or 2butanone. However, effects related to the self-association of alcohols and to solvation between unlike molecules are of minor importance when are compared with those which arise from dipolar interactions. Physical interactions are more relevant in mixtures with longer 1-alkanols. The studied systems are characterized by large structural effects. The variation of the molar excess enthalpy with the alcohol size along systems with a given ketone, or with the alkanone size in solutions with a given alcohol are discussed in terms of the different contributions to this excess function. Mixtures with methanol show rather large orientational effects. The random mixing hypothesis is attained in large extent for mixtures with 1-alkanols ≠ methanol and 2alkanones. Steric effects and cyclization lead to stronger orientational effects in mixtures with 3pentanone, 4-heptanone or cyclohexanone. The increase of temperature weakens orientational effects. Results from CC (0) S calculations show that homocoordination is predominant and support conclusions obtained from the Flory model,

Fluid Phase Equilibria, 2007

The binodal curves of the liquid–liquid equilibria (LLE) for systems of o-toluidine with heptane,... more The binodal curves of the liquid–liquid equilibria (LLE) for systems of o-toluidine with heptane, octane, nonane, decane or dodecane have been determined visually. All the curves show an upper critical solution temperature (UCST), which increases with the chain length of the alkane. The bimodal curves have a rather flat horizontal top and their symmetry depends on the chain length of

Journal of Solution Chemistry, 2020

Densities, , and kinematic viscosities, , have been determined at atmospheric pressure and at 293... more Densities, , and kinematic viscosities, , have been determined at atmospheric pressure and at 293.15-303.15 K for binary mixtures formed by methanol and one linear polyether of the type CH 3-O-(CH 2 CH 2 O) n-CH 3 (n = 2, 3, 4). Measurements on and were carried out, respectively, using an Anton Paar DMA 602 vibrating-tube densimeter and an Ubbelohde viscosimeter. The values were used to compute excess molar volumes, V E m , and, together with the results, dynamic viscosities (). Deviations from linear dependence on mole fraction for viscosity, Δ , are also provided. Different semi-empirical equations have been employed to correlate viscosity data. Particularly, the equations used are the: Grunberg-Nissan, Hind, Frenkel, Katti-Chaudhri, McAllister and Heric. Calculations show that better results are obtained from the Hind equation. The V E m values are large and negative and contrast with the positive excess molar enthalpies, H E m , available in the literature, for these systems. This indicates that structural effects are dominant. The Δ results are positive and correlate well with the difference in volumes of the mixture compounds, confirming the importance of structural effects. The temperature dependences of and of the molar volume have been used to calculate enthalpies, entropies and Gibbs energies, ΔG * , of viscous flow. It is demonstrated that ΔG * is essentially determined by enthalpic effects. Methanol + CH 3-O-(CH 2 CH 2 O) n-CH 3 mixtures have been treated in the framework of the ERAS model. Results for H E m are acceptable, while the composition dependence of the V E m curves is poorly represented. This has been ascribed to the existence of strong dipolar and structural effects in the present solutions.

The Journal of Chemical Thermodynamics, 2015

Abstract Densities, ρ , kinetic viscosities, ν , and refractive indices, n D , have been measured... more Abstract Densities, ρ , kinetic viscosities, ν , and refractive indices, n D , have been measured for (1-heptanol or 1-decanol + cyclohexylamine) systems at T = (293.15 to 303.15) K. The experimental ρ , ν , n D values were obtained using an Anton Paar DMA 602 vibrating-tube densimeter, an Ubbelohde viscosimeter and a refractometer model RMF970, respectively. These data are used to determine a number of derived properties: excess molar volumes, V m E , dynamic viscosities, η , deviations of this magnitude from linear dependence on mole fraction, Δ η , Gibbs energies of activation of viscous flow, Δ G ∗ , deviations of n D from the ideal state, Δ n D , or molar refractions, R m . In addition, (1-alkanol + cyclohexylamine) mixtures have been studied by means of the ERAS model. The corresponding parameters are reported. Viscosity data have been correlated by the following semi-empirical equations: Grunberg–Nissan, Hind, Frenkel, Katti–Chaudhri, Tamura–Kurata, Teja–Rice, McAllister and Heric. The deviations obtained are usually lower than 2%. The large negative V m E values of the studied solutions reveal the existence of strong alcohol-amine interactions. The properties V m E and R m increase with the increasing of the chain length of the 1-alcohol, while Δ η and Δ n D decrease. These variations suggest that interactions between unlike molecules are weakened and dispersive interactions become more important when the alcohol size increases. On the other hand, Δ G ∗ is essentially determined by enthalpic effects. The effect of replacing cyclohexylamine by an isomeric amine, hexylamine (HxA), dipropylamine (DPA) or N,N,N-triethylamine (TEA) in mixtures with a given 1-alkanol is also investigated. It is shown that the strength of the methanol-amine interactions become stronger in the sequence: TEA ≈ cyclohexylamine. The application of the ERAS model to (1-alcohol + cyclohexylamine) mixtures supports these findings. The parameters obtained in this work fit well into the general ERAS treatment of (1-alkanol + amine) systems.

Fluid Phase Equilibria, 2007