UNIQUAC Activity Coefficient Research Articles

Constructing and validating ternary phase diagrams as basis for polymer dissolution recycling

One of the recycling methods for polymer waste is the dissolution-precipitation process, which is based on dissolving the polymer in a suitable solvent followed by contaminant removal by, optionally filtration, and polymer precipitation through the addition of a nonsolvent. As showcased for poly(vinyl chloride) (PVC), a polymer used in the construction sector and for packaging, the current work makes clear that the less studied ternary phase diagrams are a very promising tool for the ideal solvent-nonsolvent selection. Such ternary phase diagrams provide compositional information concerning the phase separation process pushing forward the dissolution-precipitation recycling technology. It is demonstrated that these diagrams can be constructed by connecting the Flory-Huggins theory, Hansen solubility parameters and UNIQUAC activity coefficients. Model validation is performed via cloud point measurements for which one can utilize labour-intensive visual inspection or, as demonstrated in this work, one can also apply dynamic light scattering and turbidimetry, with the latter as the preferred method that is cheaper and faster. Ternary phase diagrams for multiple solvent-nonsolvent systems are theoretically constructed and experimentally validated, considering cyclohexanone-ethanol and THF-ethanol as solvent-nonsolvent pairs. It follows that PVC phase diagrams are inherently different compared to other, more commonly studied polymers, such as polyethersulfone (PES) and that for PVC the addition of a ternary interaction parameter might be required.

Thermodynamic modelling of wax precipitation using PC-SAFT in a multi-solid framework

In this work, a multi-solid approach is used for wax precipitation modelling with PC-SAFT. A vapour/liquid/solids calculation is performed for determination of wax precipitation weight percent. Beside this, the proposed model is applied to predict the wax appearance temperature (WAT) for the published oil samples experimental precipitation data. The PC-SAFT parameters for petroleum plus fractions are estimated with reliable correlations. Finally, the results of modelling are compared with the results of Lira-Galeana et al. (1996), Pedersen et al. (1991), Dalirsefat and Feyzi (2007) models and a recent work of the authors using a solid solution approach with PC-SAFT plus UNIQUAC activity coefficients according to Bagherinia et al. (2016). The results demonstrate progress in accuracy and propose the model as an acceptable predictive tool. The average absolute deviations percent for WAT estimation over all fluid samples is 0.2, in comparison with 0.55 for the recently published modelling approach (Bagherinia et al., 2016). [Received: March 3, 2017; Accepted: June 28, 2017]

Thermodynamic modelling of wax precipitation using PC-SAFT in a multi-solid framework

In this work, a multi-solid approach is used for wax precipitation modelling with PC-SAFT. A vapour/liquid/solids calculation is performed for determination of wax precipitation weight percent. Beside this, the proposed model is applied to predict the wax appearance temperature (WAT) for the published oil samples experimental precipitation data. The PC-SAFT parameters for petroleum plus fractions are estimated with reliable correlations. Finally, the results of modelling are compared with the results of Lira-Galeana et al. (1996), Pedersen et al. (1991), Dalirsefat and Feyzi (2007) models and a recent work of the authors using a solid solution approach with PC-SAFT plus UNIQUAC activity coefficients according to Bagherinia et al. (2016). The results demonstrate progress in accuracy and propose the model as an acceptable predictive tool. The average absolute deviations percent for WAT estimation over all fluid samples is 0.2, in comparison with 0.55 for the recently published modelling approach (Bagherinia et al., 2016). [Received: March 3, 2017; Accepted: June 28, 2017]

Isobaric vapor liquid equilibria data for the binary system (glycidyl butyrate + acetone, glycidyl butyrate + carbon tetrachloride, glycidyl butyrate + chloroform) at atmospheric pressure 101 kPa

Isobaric vapor liquid equilibria (VLE) for the binary mixtures of glycidyl butyrate(1) + acetone(2), glycidyl butyrate(1) + carbon tetrachloride(2) and glycidyl butyrate(1) + chloroform(2) at 101 kPa were studied. The experimental data were satisfactorily correlated with the models of Wilson, NRTL and UNIQUAC activity coefficients. The activity coefficients for the equilibrium data were obtained by the nonlinear least square method. The average relative deviations between experimental temperatures and calculated temperatures by the Wilson, NRTL and UNIQUAC models were 0.16, 0.16, 0.23% for glycidyl butyrate(1) + chloroform( 2), 0.38, 0.12, 0.27% for glycidylbutyrate(1) + carbon tetrachloride(2), and 0.67, 0.13, 0.54% for glycidyl butyrate(1) + acetone(2). Azeotrope behavior was not found for these systems. The thermodynamic consistency of the correlations was checked by the Herrington’s area test.

Removal of aromatic hydrocarbons from hydrocarbon mixture using glycols at 303.15 K and 333.15 K and atmospheric pressure: Experimental and calculated data by NRTL and UNIQUAC models

Aromatic hydrocarbons are usually extracted from reformed naphtha, which are multicomponent mixtures with aliphatic hydrocarbons. These components have very close boiling point, which makes distillation process not so efficient and economically infeasible. For this reason, aromatics compounds are usually separated from aliphatic compounds by intermediate of solvent extraction unit operation. In this work, liquid–liquid equilibrium (LLE) data for systems containing decane+toluene+diethylene glycol (DEG) and decane+toluene+triethylene glycol (TEG) at T=(303.15 and 333.15)K and atmospheric pressure were studied. It was observed that temperature hardly influence the size of the two-phase region. Distribution coefficient and selectivity have been calculated from those experimental data. For all systems studied, selectivity parameter showed values greater than 1 indicating that the extraction is possible by using DEG and TEG as extractor solvents. Additionally, selectivity values ​​increase with increasing glycol carbon chain. LLE have been correlated by intermediate of NRTL and UNIQUAC activity coefficients.

Mutual solubility of binary mixtures of octadecane with diethanolamine and bis-hydroxyethyl piperazine

Liquid-liquid equilibria were determined by the cloud point method for the diethanolamine-octadecane and hydroxyethyl piperazine-octadecane systems. The results were successfully interpreted using NRTL, UNIQUAC and van Laar activity coefficient models. The NRTL parameters were also used to predict vapor-liquid equilibria.