Superposition of Liquid–Liquid and Solid–Liquid Equilibria of Linear and Branched Molecules: Binary Systems

Abstract

Crystallization from solution is a promising unit operation to separate linear and branched isomers. To reduce the number of experiments, a thermodynamic modeling approach is proposed to calculate the required phase equilibria. Hereby, the thermodynamic data of pure substances are required to fit model parameters, but the branched isomers are often not available. Therefore, a methodology which allows for the prediction of phase equilibria of systems containing branched molecules was developed in this contribution. The basic idea is to fit the model parameters to experimental data of linear molecules and combine these parameters with information about the molecular architecture of the branched isomers to predict the phase equilibria of these isomers. For this purpose the lattice cluster theory which considers directly the molecular architecture was applied in combination with the chemical association lattice model. As model systems linear and branched alkanes dissolved in an alcohol were investigated. The developed methodology is able to predict the binary liquid–liquid equilibria of the branched alkanes dissolved in an alcohol in good agreement to experimental data. Furthermore, the thermodynamic model is able to simultaneously calculate the liquid–liquid equilibrium and the solid–liquid equilibrium with the same model parameters in good agreement with experimental data.

Oiling‐Out Crystallization of Beta‐Alanine on Solid Surfaces Controlled by Solvent Exchange

“…Solubility phase diagram of the compound, the good solvent and the antisolvent provides a guideline for determination of the solvent ratio for crystallization. [ 10,19,26,29,30 ] Lately, researchers started looking closely into the interface between the two liquid phases, [ 31–33 ] where the mass transfer and heat transfer occur, directly influencing formation of the droplets and crystallization.…”

Adsorption Isotherms of Liquid Isomeric Mixtures

“…The lattice coordination number z was chosen to be 6 in accordance with earlier publications. , ε/ k B T is defined as …”

“…The lattice cluster theory (LCT) developed by Freed and co-workers − directly considers the molecular architecture within the Helmholtz free energy, where the molecular architecture is defined by architectural coefficients from the chemical formula. The LCT was successfully applied for the prediction of solid–liquid–liquid equilibria of mixtures made of linear alkanes, branched alkanes, and methanol or ethanol and the corresponding binary subsystems . Additionally, the phase behavior of mixtures containing hyperbranched polymers could be modeled successfully. − Upon introduction of empty lattice sites, also compressible mixtures can be described .…”

Oiling-out Crystallization of Beta-Alanine onSolid Surfaces Controlled by Solvent Exchange

“…For given pair of the good solvent and the antisolvent, the solvent ratio is essential to control the path of the phase separation. Solubility phase diagram of the compound, the good solvent and the the antisolvent provides a guideline for determination of the solvent ratio for crystallization 10,19,26,29,30 . Lately, researchers started looking closely into the interface between the two liquid phases [31][32][33] , where the mass transfer and heat transfer occur, directly influencing formation of the droplets and crystallization.…”