Capabilities and Limitations of an Association Theory for Chemicals in Liquid or Supercritical Solvents

Tsivintzelis, Ioannis; Kontogeorgis, Georgios M.

doi:10.1021/ie301388d

Cited by 19 publications

(14 citation statements)

References 106 publications

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“…Many researchers have conducted studies with SAFT variants for modeling acetic acid properties and its mixtures, [8][9][10][11][12][13][14][15][16][17][18][19][20] especially using the PC-SAFT and CPA equations of state (EOS).…”

Section: Introductionmentioning

confidence: 99%

Extensive Study of the Capabilities and Limitations of the CPA and sPC-SAFT Equations of State in Modeling a Wide Range of Acetic Acid Properties

Ribeiro

Alberton

Paredes

et al. 2018

Ind. Eng. Chem. Res.

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The accurate description of many thermodynamic properties of acetic acid and its mixtures can be a challenge to model with standard thermodynamic models like local-composition activity coefficient models and cubic equations of state. A possible solution is offered by association equations of state, e.g. those belonging to the Statistical Associating Fluid Theory (SAFT) family. While several researchers have studied the use of SAFT variants to model acetic acid properties (pure compound and mixtures), with few exceptions, those studies focused exclusively on phase equilibria including vapor pressure and density. Other important properties, such as the speed of sound, second virial coefficient, compressibility factor, enthalpy of vaporization, and the isobaric heat capacity have not been considered yet. Few studies investigate which is the appropriate association scheme to be used for acetic acid. In this work, we compare the capability of two association models, Cubic Plus Association (CPA) and simplified Perturbed-Chain SAFT (sPC-SAFT), to predict a wide range of properties of acetic acid (mixtures) including derivative properties. We evaluate the influence of including one or more of those properties in the parameter estimation procedure for sPC-SAFT, we compare the results obtained with various choices of the association schemes (one or two sites) and finally we evaluate the efficiency of CPA and sPC-SAFT in correlating the phase equilibria of the binary mixtures of acetic acid with water, hexane or ethanol. It is concluded that both equations of state perform overall similarly, with the one-site scheme performing better overall, especially for some properties. The results of the evaluation also show that some properties are inter-correlated in the parameter estimation process making it essentially impossible to obtain sets that can accurately describe all the properties of acetic acid.

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Section: Introductionmentioning

confidence: 99%

Extensive Study of the Capabilities and Limitations of the CPA and sPC-SAFT Equations of State in Modeling a Wide Range of Acetic Acid Properties

Ribeiro

Alberton

Paredes

et al. 2018

Ind. Eng. Chem. Res.

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“…In the context of CPA, we have previously carried out several studies with polar systems (acetates, ketones, esters, ethers …..) in mixtures with water, inert compounds, etc. where multicomponent and multiphase equilibria have been considered [76][77][78]. In all cases the predictions have been satisfactory without additional polar terms.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 80%

“…In all cases the predictions have been satisfactory without additional polar terms. Earlier some researchers [81,4] have treated polar compounds like acetone as pseudo-associating but, while this approach is as satisfactory as an explicit treatment of polarity in mixtures with hydrocarbons, the results are not very satisfactory for multicomponent systems [77] and is thus not recommended. Even for binary systems, sometimes, e.g.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

Recent advances with association models for practical applications

2018

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Association models like CPA and other SAFT variants have found widespread use, especially over the recent 30 or so years, and this is not limited any more to universities and researchers. Industry is beginning slowly to adopt such models for some applications and a few of the association models are now provided by commercial simulators. Association models account explicitly for hydrogen bonding (and other complex) phenomena and for this reason they are potentially more useful and more successful than traditional models like cubic equations of state and activity coefficient models. Still, for practical applications all models are judged by their results and these depend on availability of experimental data, the number and type of adjustable parameters and the performance of the models for phase equilibria and occasionally also for other properties. We will consider four case studies in this work which will illustrate some of the capabilities and limitations of these association models in different applications. We will offer a "model developer's" point of view showing in several cases all stages of model development in order to illustrate what worked, what didn't and how it was corrected (when possible). The "physics" and "application" aspects of the models will be in all cases discussed. All results will be shown with the CPA equation of state, although we expect that the overall conclusions will be the same for a wide range of association models.

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“…Such association schemes, often result in successful description of the vapor-liquid equilibrium of carboxylic acid mixtures 2,[23][24][25] , however, present serious limitations in aqueous solutions, the description of liquidliquid equilibrium and more demanding calculations, such as the description of thermal properties. 1,2 Only recently, the association term of both types of models was extended in order to describe the dimerization of organic acids in a more realistic way. [27][28][29][30] Most often, in order to test the validity of a model, its predictions are compared solely to phase equilibrium data.…”

Section: Introductionmentioning

confidence: 99%

Dimerization of Carboxylic Acids: An Equation of State Approach

2017

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The association term of the nonrandom hydrogen bonding theory, which is an equation of state model, is extended to describe the dimerization of carboxylic acids in binary mixtures with inert solvents and in systems of two different acids. Subsequently, the model is applied to describe the excess enthalpies and the vapor-liquid equilibrium of relevant binary mixtures containing low molecular weight organic acids. The model sheds light on the interplay of intermolecular interactions through the calculation of the various contributions to the mixing enthalpies, namely from hydrogen bonding and non-hydrogen bonding (dipolar, induced polar or dispersive) interactions. According to model predictions, the acid molecules are so strongly associated that the addition of inert solvents to carboxylic acids with small carbon numbers at ambient temperature does not dramatically alter their degree of association. Consequently, the observed endothermic dissolution process is mainly attributed to the hindering of polar interactions. Furthermore, upon mixing of two carboxylic acids, the rearrangement of hydrogen bonds due to the formation of cross associating species results in an insignificant contribution to the heats of mixing due to the rather constant dimerization enthalpy that is revealed by the available experimental data for low molecular weight compounds.

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Capabilities and Limitations of an Association Theory for Chemicals in Liquid or Supercritical Solvents

Cited by 19 publications

References 106 publications

Extensive Study of the Capabilities and Limitations of the CPA and sPC-SAFT Equations of State in Modeling a Wide Range of Acetic Acid Properties

Extensive Study of the Capabilities and Limitations of the CPA and sPC-SAFT Equations of State in Modeling a Wide Range of Acetic Acid Properties

Recent advances with association models for practical applications

Dimerization of Carboxylic Acids: An Equation of State Approach

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