Application of the CPA equation of state to organic acids

Derawi, Samer; Zeuthen, Jacob Hjerrild; Michelsen, Michael Locht; Stenby, Erling Halfdan; Kontogeorgis, Georgios M.

doi:10.1016/j.fluid.2004.08.021

Cited by 61 publications

(104 citation statements)

References 18 publications

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“…In the hexanoic acid/water mixture exists the cross-association, and the binary interaction parameter is estimated a negative value for all models. Derawi et al 42 investigated the LLE for acetic acid/decane, and their result using CPA model gives a graphically similar result to our work.…”

Section: ■ Theoretical Backgroundsupporting

confidence: 87%

Liquid–Liquid Equilibrium of Associating Fluid Mixtures Using Perturbed-Hard-Sphere-Chain Equation of State Combined with the Association Model

Lee

Kim

2014

Ind. Eng. Chem. Res.

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Perturbed-hard-sphere-chain-association (PHSC-AS) equation of state, which is defined by incorporating the association term of the statistical associating fluid theory (SAFT) model into the PHSC equation of state with van der Waals-type dispersion term, is used to calculate the liquid−liquid equilibrium (LLE) for complex associating mixtures such as alcohol/alkane, water/alkane, acetic acid/alkane, alcohol/water, and carboxylic acid/water systems. In this work, the PHSC-AS models with two different chain terms have been investigated. One is the original model proposed by Song et al. [Macromolecules 1994, 27 (2), 441−448], and the other is the modified model whose chain term was replaced with that of the SAFT model. The calculated results of LLE for associating mixtures are compared with those by the purturbed-chain-SAFT (PC-SAFT) model as well. The results with PHSC-AS and PC-SAFT equation of state are in acceptable agreement with the experimental data. Despite the simple dispersion equation with van der Waals-type, PHSC-AS models show a reasonable calculation performance for LLE of associating fluid mixture. ■ INTRODUCTIONThe calculation of liquid−liquid equilibria (LLE) is of importance in the design and development of new separation processes, such as extraction and extractive distillation, and is also a challenge for nonideal mixtures with strong attractive interaction owing to hydrogen bonding. For accurate process modeling and design, the reliable model for associating fluids is essentially required and important.A great number of theoretical studies (i.e., excess Gibbs energy models, conductor-like screening model (COSMO)-based model, and equation of state (EOS)) have been mainly focused on theoretical models to account for the effects of solvation and association on the bulk properties and phase behaviors. Correlations of LLE has been done usually by using the excess Gibbs free energy (g E ) models, such as nonrandom two-liquid (NRTL), 1 universal quasichemical (UNIQUAC), 2 and UNIQUAC functional-group activity coefficients (UNI-FAC), 3 which have been successfully applied for the prediction and correlation of several liquid−liquid systems. The UNIFAC model is most extensively used as a predictive model because of the universal binary interaction parameters between each functional group. 4−6 More recently, COSMO-based models obtained from the results of quantum mechanical calculations, such as COSMO-RS (real solvents) 7,8 and COSMO-SAC (segment activity coefficient), 9,10 have been shown to provide reliable predictions for the various thermodynamic properties for many molecules. 11,12 Aside from excess Gibbs free energy models, the EOS provides a useful tool for describing phase equilibria of mixtures regardless of magnitude of pressure. The advance in statistical mechanics results in perturbation theories capable of accurately describing the thermodynamic properties for nonideal fluids. Wertheim 13,14 proposed the thermodynamic perturbation theory (TPT1) for hydrogen bonding fluids. The statistical-asso...

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Section: ■ Theoretical Backgroundsupporting

confidence: 87%

Liquid–Liquid Equilibrium of Associating Fluid Mixtures Using Perturbed-Hard-Sphere-Chain Equation of State Combined with the Association Model

Lee

Kim

2014

Ind. Eng. Chem. Res.

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“…Carboxylic acids are known to form dimers in the vapor phase at very low pressures and moderate temperatures. CPA has been recently extended to binary systems containing carboxylic acids [11]. CPA has been used in this work to model LLE for the acetic acid-water-hexane system at 298 K and 1 bar.…”

Section: Application Of Cpa To Multicomponent Systems Containing Carbmentioning

confidence: 99%

Recent applications of the cubic-plus-association (CPA) equation of state to industrially important systems

Folas

Derawi

Michelsen

et al. 2005

Fluid Phase Equilibria

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“…The importance of appropriate association scheme was extensively discussed only in the case of carboxylic acids which oscillate between 2B model and 1A model (in which molecules contain only a single site which is a model adequate for diluted systems in which the carboxylic groups form cyclic dimers). [50][51][52] Biomass based products are more and more used as substituent of petroleum fluids, both as fuels and as raw materials for the chemical industry. 53 The bio-oils are complex mixtures with a high content of oxygenated compounds containing mainly hydroxyl, carbonyl, ether, and carboxyl groups, i.e., groups which can participate on hydrogen bonding.…”

Section: Introductionmentioning

confidence: 99%

Size distribution of associated clusters in liquid alcohols: Interpretation of simulation results in the frame of SAFT approach

Janeček

Paricaud

2013

The Journal of Chemical Physics

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The size distribution and topology of associated clusters for primary alcohols is studied using molecular dynamics simulations. Liquid ethanol, propanol, butanol, hexanol, and octanol are simulated at pressure P = 1 bar and temperatures T = 300 K, T = 350 K, and T = 400 K. The fractions of molecules with different sets of hydrogen bonded partners, the size of associated cluster and the site-site distribution functions between atoms participating on hydrogen bonding are extracted from simulated trajectories. For all alcohols longer than ethanol, the length of the alkyl chain has only a marginal effect on the association. Consequently, related properties like coordination numbers of hydroxyl group, size distribution of associates, or fractions of differently coordinated alcohol molecules are independent on the molecular size. Although we employed a force-field without involved polarizability, we observe a positive cooperativity of hydrogen bonding simply as a consequence of steric and electrostatic interactions. The size and topology of associates is analyzed within the frame of 3B model of statistical association fluid theory. Although this approach enables good thermodynamic description of systems containing associating compounds, several insufficiencies appear in the description at molecular level. © 2013 AIP Publishing LLC.[http://dx.doi.org/10.1063/1.4827107]

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Application of the CPA equation of state to organic acids

Cited by 61 publications

References 18 publications

Liquid–Liquid Equilibrium of Associating Fluid Mixtures Using Perturbed-Hard-Sphere-Chain Equation of State Combined with the Association Model

Liquid–Liquid Equilibrium of Associating Fluid Mixtures Using Perturbed-Hard-Sphere-Chain Equation of State Combined with the Association Model

Recent applications of the cubic-plus-association (CPA) equation of state to industrially important systems

Size distribution of associated clusters in liquid alcohols: Interpretation of simulation results in the frame of SAFT approach

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