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Troncoso J, González-Salgado D. The temperature of maximum density for aqueous solutions. J Chem Phys 2024; 160:100902. [PMID: 38465676 DOI: 10.1063/5.0180094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2023] [Accepted: 12/26/2023] [Indexed: 03/12/2024] Open
Abstract
Experimental and theoretical advances for understanding the temperature of maximum density (TMD) of aqueous solutions are outlined. The main equations that relate the TMD behavior to key thermodynamic properties are stated. The experimental TMD data are classified as a function of the nature of the solute (inorganic electrolytes, non-electrolytes, organic salts and ionic liquids, and amino acids and proteins). In addition, the experimental results that explore the effect of pressure are detailed. These experimental data are rationalized by making use of qualitative and semi-quantitative arguments based on the thermodynamics of aqueous systems. The main theoretical and simulation advances in TMD for aqueous solutions are also shown-including new calculations in the context of the scaled particle theory-and their ability to reproduce the experimental data is evaluated. Finally, new experiments and theoretical and simulation developments, which could give important insights into the problem of TMD for aqueous solutions, are proposed.
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Affiliation(s)
- Jacobo Troncoso
- Instituto de Física e Ciencias Aeroespaciais da Universidade de Vigo and Unidad MSMN Asociada al CSIC por el IQF Blas Cabrera, Ourense 32004, Spain
| | - Diego González-Salgado
- Instituto de Física e Ciencias Aeroespaciais da Universidade de Vigo and Unidad MSMN Asociada al CSIC por el IQF Blas Cabrera, Ourense 32004, Spain
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2
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Gómez-Álvarez P, Noya EG, Lomba E. Structural study of water/alcohol mixtures adsorbed in MFI and MEL porosils. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.120527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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3
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Martínez-Jiménez M, Benavides AL. The liquidus temperature curve of aqueous methanol mixtures: a numerical simulation study. J Chem Phys 2022; 157:104502. [DOI: 10.1063/5.0099751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The liquidus temperature curve that characterizes the boundary between the liquid methanol/water mixture and its coexistence with ice Ih is determined using the direct-coexistence method. Several methanol concentrations and pressures of 0.1 MPa, 50 MPa, and 100 MPa are considered. In this study, we used the TIP4P/Ice model for water and two different models for methanol: OPLS and OPLS/2016, using the geometric rule for the Lennard-Jones cross interactions. We compared our simulation results with available experimental data and found that this combination of models reproduces reasonably well the liquidus curve for methanol mole fractions up to xm=0.3 at p=0.1 MPa. The freezing point depression of these mixtures is calculated and compared to experimental results. We also analyzed the effect of pressure on the liquidus curve, and we found that both models also reproduce qualitatively well the experimental decreasing of the liquidus temperatures as the pressure increases.
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Affiliation(s)
| | - Ana Laura Benavides
- Ingeniería Física, Universidad de Guanajuato División de Ciencias e Ingenierías Campus León, Mexico
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Hernandes VF, Marques MS, Bordin JR. Phase classification using neural networks: application to supercooled, polymorphic core-softened mixtures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 34:024002. [PMID: 34638114 DOI: 10.1088/1361-648x/ac2f0f] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 10/12/2021] [Indexed: 06/13/2023]
Abstract
Characterization of phases of soft matter systems is a challenge faced in many physical chemical problems. For polymorphic fluids it is an even greater challenge. Specifically, glass forming fluids, as water, can have, besides solid polymorphism, more than one liquid and glassy phases, and even a liquid-liquid critical point. In this sense, we apply a neural network algorithm to analyze the phase behavior of a mixture of core-softened fluids that interact through the continuous-shouldered well (CSW) potential, which have liquid polymorphism and liquid-liquid critical points, similar to water. We also apply the neural network to mixtures of CSW fluids and core-softened alcohols models. We combine and expand methods based on bond-orientational order parameters to study mixtures, applied to mixtures of hardcore fluids and to supercooled water, to include longer range coordination shells. With this, the trained neural network was able to properly predict the crystalline solid phases, the fluid phases and the amorphous phase for the pure CSW and CSW-alcohols mixtures with high efficiency. More than this, information about the phase populations, obtained from the network approach, can help verify if the phase transition is continuous or discontinuous, and also to interpret how the metastable amorphous region spreads along the stable high density fluid phase. These findings help to understand the behavior of supercooled polymorphic fluids and extend the comprehension of how amphiphilic solutes affect the phases behavior.
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Affiliation(s)
- V F Hernandes
- Programa de Pós-Graduação em Física, Departamento de Física, Instituto de Física e Matemática, Universidade Federal de Pelotas, Caixa Postal 354, 96001-970, Pelotas-RS, Brazil
| | - M S Marques
- Centro das Ciências Exatas e das Tecnologias, Universidade Federal do Oeste da Bahia Rua Bertioga, 892, Morada Nobre, CEP 47810-059, Barreiras-BA, Brazil
| | - José Rafael Bordin
- Departamento de Física, Instituto de Física e Matemática, Universidade Federal de Pelotas, Caixa Postal 354, 96001-970, Pelotas-RS, Brazil
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Marques MS, Hernandes VF, Lomba E, Bordin JR. Competing interactions near the liquid-liquid phase transition of core-softened water/methanol mixtures. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2020.114420] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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6
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Perrin CL, Shrinidhi A. Enthalpic and entropic contributions to the basicity of cycloalkylamines. Chem Sci 2020; 11:8489-8494. [PMID: 34123109 PMCID: PMC8163384 DOI: 10.1039/d0sc02931a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Large-ring cycloalkylamines are slightly less basic than other cycloalkylamines such as cyclohexylamine, even though all have tetrahedral carbons and are strain-free. To understand why, enthalpy and entropy for protonation of a series of cycloalkylamines were accurately determined by isothermal titration calorimetry in 3 : 1 methanol–water. The study required resolving a discrepancy between these measurements and those in pure water. The data show that the lower basicity of large-ring cycloalkylamines is not due to enthalpy but to a more negative entropy of protonation. Computations show that this can be attributed in part to an entropy of conformational mixing, but the dominant contribution is steric hindrance to solvation, also corroborated by computation. Large-ring cycloalkylamines are slightly less basic than other cycloalkylamines such as cyclohexylamine, even though all have tetrahedral carbons and are strain-free.![]()
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Affiliation(s)
- Charles L. Perrin
- Department of Chemistry & Biochemistry
- University of California—San Diego
- La Jolla
- USA
| | - Annadka Shrinidhi
- Department of Chemistry & Biochemistry
- University of California—San Diego
- La Jolla
- USA
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7
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Pršlja P, Lomba E, Gómez-Álvarez P, Urbič T, Noya EG. Adsorption of water, methanol, and their mixtures in slit graphite pores. J Chem Phys 2019; 150:024705. [PMID: 30646695 PMCID: PMC6910600 DOI: 10.1063/1.5078603] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 12/19/2018] [Indexed: 11/15/2022] Open
Abstract
The behavior of water, methanol, and water-methanol mixtures confined in narrow slit graphite pores as a function of pore size was investigated by Monte Carlo, hybrid Monte Carlo, and Molecular Dynamics simulations. Interactions were described using TIP4P/2005 for water, OPLS/2016 for methanol, and cross interactions fitted to excess water/methanol properties over the whole range of concentrations, which provide a rather accurate description of water-methanol mixtures. As expected for hydrophobic pores, whereas pure methanol is adsorbed already from the gas phase, pure water only enters the pore at pressures well beyond bulk saturation for all pore sizes considered. When adsorbed from a mixture, however, water adsorbs at much lower pressures due to the formation of hydrogen bonds with previously adsorbed methanol molecules. For all studied compositions and pore sizes, methanol adsorbs preferentially over water at liquid-vapor equilibrium conditions. In pure components, both water and methanol are microscopically structured in layers, the number of layers increasing with pore size. This is also the case in adsorbed mixtures, in which methanol has a higher affinity for the walls. This becomes more evident as the pore widens. Diffusion of pure water is higher than that of pure methanol for all pore sizes due to the larger size of the methyl group. In mixtures, both components present similar diffusivities at all pore sizes, which is explained in terms of the coupling of molecular movements due to strong hydrogen bonding between methanol and water molecules. This is particularly evident in very narrow pores, in which pure methanol diffusion is completely impeded on the time scale of our simulations, but the presence of a small amount of water molecules facilitates alcohol diffusion following a single-file mechanism. Additionally, our results indicate that pure water diffusivities display a non-monotonous dependence of pore size, due to effects of confinement (proximity to a fluid-solid-fluid transition induced by confinement as reported in previous work) and the dynamic anomalies of water.
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Affiliation(s)
- Paulina Pršlja
- Institute of Physical Chemistry "Rocasolano," Serrano 119, E-28006 Madrid, Spain
| | - Enrique Lomba
- Institute of Physical Chemistry "Rocasolano," Serrano 119, E-28006 Madrid, Spain
| | - Paula Gómez-Álvarez
- Institute of Physical Chemistry "Rocasolano," Serrano 119, E-28006 Madrid, Spain
| | - Tomaz Urbič
- Faculty of Chemistry and Chemical technology, University of Ljubljana, Ljubljana, Slovenia
| | - Eva G Noya
- Institute of Physical Chemistry "Rocasolano," Serrano 119, E-28006 Madrid, Spain
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Gómez-Álvarez P, Noya EG, Lomba E, Valencia S, Pires J. Study of Short-Chain Alcohol and Alcohol-Water Adsorption in MEL and MFI Zeolites. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:12739-12750. [PMID: 30296099 DOI: 10.1021/acs.langmuir.8b02326] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In this paper, we present a comparative study of the adsorption behavior of short chain alcohols (pure and in aqueous solution) into silicalite-1 (MFI-type zeolite) and silicalite-2 (MEL-type zeolite). For quite some time, silicalite-1 has been the reference material to address the problem of adsorptive-based separation, mostly for hydrocarbon mixtures. Interestingly, being structurally close to silicalite-1, adsorption studies using silicalite-2 are scarce and to the best of our knowledge, a comparative study of their behavior for alcohol-water mixtures has not been published to date. We have here resorted to molecular simulation techniques to analyze the adsorption and diffusion phenomena in both zeolites at 25 and 50 °C for pure methanol, ethanol, 1-butanol, and water, and for some relevant compositions of alcohol/water mixtures. In addition to the dilute regime in the mixture, our study ranges from intermediate alcohol concentrations to alcohol-rich phases, relevant to alcohol purification processes. Besides, we have performed volumetric and calorimetric measurements of single-component adsorption of alcohols in pure silica MEL zeolite, which were used to validate the model potentials used in the simulations. We observe that the zigzag channels of MFI zeolite are most likely responsible for its somewhat higher affinity for alcohols. This leads to higher adsorption selectivities when compared to those of MEL zeolite. We have also found that the choice of water model strongly conditions water coadsorption into the zeolites and subsequently the predictions of the adsorbent's selectivity in alcohol/water systems. Despite considerable differences for adsorbed pure components, diffusivities of alcohol and water adsorbed from mixtures are relatively similar, as a consequence of the strong hydrogen bonds between hydroxyl groups and water.
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Affiliation(s)
- Paula Gómez-Álvarez
- Instituto de Química Física Rocasolano, CSIC , Serrano 119 , E-28006 Madrid , Spain
| | - Eva G Noya
- Instituto de Química Física Rocasolano, CSIC , Serrano 119 , E-28006 Madrid , Spain
| | - Enrique Lomba
- Instituto de Química Física Rocasolano, CSIC , Serrano 119 , E-28006 Madrid , Spain
| | - Susana Valencia
- Instituto de Tecnología Química , Universitat Politècnica de València-CSIC , Avenida de los Naranjos, s/n , Valencia 46022 , Spain
| | - João Pires
- CQB and CQE, Departamento de Química e Bioquímica, Faculdade de Ciências , Universidade de Lisboa , Ed. C8 , Campo Grande , 1749-016 Lisboa , Portugal
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9
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Abstract
Methanol is the simplest alcohol and possible energy carrier because it is easier to store than hydrogen and burns cleaner than fossil fuels. It is a colorless liquid, completely miscible with water and organic solvents and is very hygroscopic. Here, simple two-dimensional models of methanol, based on Mercedes-Benz (MB) model of water, are examined by Monte Carlo simulations. Methanol particles are modeled as dimers formed by an apolar Lennard-Jones disk, mimicking the methyl group, and a sphere with two hydrogen bonding arms for the hydroxyl group. The used models are the one proposed by Hribar-Lee and Dill (Acta Chimica Slovenica, 53:257, 2006.) with the overlapping discs and a new model with tangentially fused dimers. The comparison was done between the models, in connection to the MB water, as well as with experimental results and with new simulations done for 3D models of methanol. Both 2D models show similar trends in structuring and thermodynamics. The difference is the most pronounced at lower temperatures, where the smaller model exhibits spontaneous crystallization, while the larger model shows metastable states. The 2D structural organization represents well the clustering tendency observed in 3D models, as well as in experiments. The models qualitatively agree with the bulk methanol thermodynamic properties like density and isothermal compressibility, however, heat capacity at the constant pressure shows trend more similar to the water behavior. This work on the smallest amphiphilic organic solute provides a simple testing ground to study the competition between polar and non-polar effects within the molecule and physical properties.
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Affiliation(s)
- Tomislav Primorac
- Faculty of Science, University of Split, Rudjera Boškovića 33, 21000 Split, Croatia
- Fakultät für Maschinenbau, Universität Paderborn, Warburger Str. 100, 33098 Paderborn, Germany
| | - Martina Požar
- Faculty of Science, University of Split, Rudjera Boškovića 33, 21000 Split, Croatia
- Laboratoire de Physique Théorique de la Matière Condensée (UMR CNRS 7600), Université Pierre et Marie Curie, 4 Place Jussieu, F75252, Paris cedex 05, France
| | - Franjo Sokolić
- Faculty of Science, University of Split, Rudjera Boškovića 33, 21000 Split, Croatia
| | - Larisa Zoranić
- Faculty of Science, University of Split, Rudjera Boškovića 33, 21000 Split, Croatia
| | - Tomaz Urbic
- Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, 1000 Ljubljana, Slovenia
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10
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Furlan AP, Lomba E, Barbosa MC. Temperature of maximum density and excess properties of short-chain alcohol aqueous solutions: A simplified model simulation study. J Chem Phys 2018; 146:144503. [PMID: 28411617 DOI: 10.1063/1.4979806] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We perform an extensive computational study of binary mixtures of water and short-chain alcohols resorting to two-scale potential models to account for the singularities of hydrogen bonded liquids. Water molecules are represented by a well studied core softened potential which is known to qualitatively account for a large number of water's characteristic anomalies. Along the same lines, alcohol molecules are idealized by dimers in which the hydroxyl groups interact with each other and with water with a core softened potential as well. Interactions involving non-polar groups are all deemed purely repulsive. We find that the qualitative behavior of excess properties (excess volume, enthalpy, and constant pressure heat capacity) agrees with that found experimentally for alcohols such as t-butanol in water. Moreover, we observe that our simple solute under certain conditions acts as a "structure-maker," in the sense that the temperature of maximum density of the bulk water model increases as the solute is added, i.e., the anomalous behavior of the solvent is enhanced by the solute.
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Affiliation(s)
- A P Furlan
- Instituto de Física, Univeridade Federal do Rio Grande do Sul, Caixa Postal 15051, 91501-570 Porto Alegre, Rio Grande do Sul, Brazil
| | - E Lomba
- Instituto de Química Física Rocasolano, CSIC, Serrano 119, E-28006 Madrid, Spain
| | - M C Barbosa
- Instituto de Física, Univeridade Federal do Rio Grande do Sul, Caixa Postal 15051, 91501-570 Porto Alegre, Rio Grande do Sul, Brazil
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11
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Kohns M, Horsch M, Hasse H. Activity coefficients from molecular simulations using the OPAS method. J Chem Phys 2017; 147:144108. [DOI: 10.1063/1.4991498] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Affiliation(s)
- Maximilian Kohns
- Laboratory of Engineering Thermodynamics, University of Kaiserslautern, Erwin-Schrödinger Str. 44, D-67663 Kaiserslautern, Germany
| | - Martin Horsch
- Laboratory of Engineering Thermodynamics, University of Kaiserslautern, Erwin-Schrödinger Str. 44, D-67663 Kaiserslautern, Germany
| | - Hans Hasse
- Laboratory of Engineering Thermodynamics, University of Kaiserslautern, Erwin-Schrödinger Str. 44, D-67663 Kaiserslautern, Germany
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