Liquid−liquid equilibrium (LLE) phase compositions (tie-line data) were experimentally measured and thermodynamically modeled for the systems nheptane + toluene + (butane-1,4-diol or glycerol) at 298.2, 313.2, and 333.2 K and 0.1 MPa. The direct analytical method was used to obtain the LLE data using a doublewalled glass cell. The phase equilibrium samples were quantitatively analyzed using gas chromatography. The ternary systems were successfully correlated using the NRTL and UNIQUAC thermodynamic models. The effectiveness of using butane-1,4-diol or glycerol as an alternative solvent to extract toluene from alkanes was evaluated by determining selectivity and solvent capacity. All systems studied were found to demonstrate type II ternary LLE behavior. The selectivity for the solvents studied was found to be comparable or superior to conventional solvents, but solvent capacities were poor, suggesting that the use of a cosolvent might be required to reduce solvent-to-feed ratios.

There is increasing focus on the replacement of commonly used solvents in the liquid−liquid extraction of aromatics with solvents that result in improved process economics as well as reduced risk in terms of health, safety, and environment. In this work, a selection of organic chemicals are proposed for further study as replacement solvents that meet the technological requirements for the process of aromatics extraction from alkanes and have not been conventionally considered previously for this application. There were 52,654 organic chemicals screened with the use of a search algorithm based on the process requirements in terms of physical properties, capacity, selectivity, and performance index. Nine organic chemicals were identified (not being previously considered) that met all the criteria imposed by the search algorithm. A risk assessment further screened the identified chemicals, filtering out the potential solvents with adverse impacts on health, safety, and environment. Process designs were developed with the use of ASPEN plus in order to ascertain the effects of solvent choice on process economics via the use of total annual costs. The screening process in this work produced significant insights due to its holistic approach. The incorporation of factors such as solvent price, solvent loss, utilities, capital costs, health, and environmental impact showed that several of the solvents identified may be sustainable and cost-effective alternatives to conventionally used solvents. This highlights the need for a robust and broad perspective in considering the impact of solvent choice.

In order to investigate the effect of using 2-methyl-2,4-pentanediol as a co-solvent to 1,4-butanediol in the extraction of toluene from n-heptane, liquid–liquid equilibrium (LLE) phase compositions (tie-line data) were experimentally measured and thermodynamically modeled for the system n-heptane + toluene + 1,4-butanediol + 2-methyl-2,4-pentanediol at 298.2 and 313.2 K and 0.1 MPa. The direct analytical method was used to obtain the LLE data using a double-walled glass cell. The phase equilibrium samples were quantitatively analyzed using gas chromatography. The quaternary systems were successfully correlated using the NRTL and UNIQUAC thermodynamic models. Selectivity and solvent capacity were evaluated at various concentrations of co-solvent and compared to that of using pure 1,4-butanediol. The pseudo-ternary systems studied were found to demonstrate type II or type I phase behavior depending on temperature and co-solvent concentration. The presence of 2-methyl-2,4-pentanediol was found to have significantly improved solvent capacity at the cost of reduced selectivity.

The design and operation of the process to extract aromatics from petroleum intermediates via solvent extraction can be enhanced in terms of efficiency by access to liquid–liquid equilibrium (LLE) data. This study serves to contribute LLE data for a heavy alkane, aromatic, and solvent mixture, which is of limited availability in the open literature. Ternary LLE phase compositions were experimentally measured and thermodynamically modeled for the systems N-formylmorpholine (NFM) + toluene + (n-nonane or n-decane) at 303.2, 323.2, and 343.2 K and 101.3 kPa. The direct analytical method was used to obtain the LLE data using a double-walled glass cell. The phase equilibrium samples were quantitatively analyzed using gas chromatography. The ternary systems were successfully correlated using the non-random two-liquid and universal quasichemical thermodynamic models. The effectiveness of using NFM as an alternative solvent to extract toluene from a mixture containing n-nonane or n-decane was evaluated by determining the selectivity. The plait point for the systems measured was determined using the graphical Coolidge method. All systems studied were found to exhibit type I ternary LLE behavior, and relative selectivity was greater than unity, indicating that the extraction of toluene from heavy alkanes is feasible using NFM.

The use of 2-methyl-2,4-pentanediol as a potential cosolvent to glycerol was studied in order to investigate its impact on solvent capacity in the separation of toluene from n-heptane via liquid−liquid extraction. To this end, quaternary liquid− liquid equilibrium (LLE) data were experimentally measured for the system n-heptane + toluene + glycerol + 2-methyl-2,4-pentanediol at 298.2 and 313.2 K and 0.1 MPa. The measurements were conducted in a double-walled glass cell using the direct analytical method, and phase compositions were analyzed via gas chromatography. The data were correlated using the NRTL and UNIQUAC models, which were able to suitably represent the tie-line compositions. At different molar ratios of solvent to cosolvent, the selectivity and solvent capacity were calculated and compared to that of using pure glycerol. It was ascertained that the pseudo-ternary systems possess type I or type II behaviors depending on the molar ratio of glycerol to 2-methyl-2,4-pentanediol. It was observed that solvent capacity is not appreciatively improved for molar ratios that exhibit type II behavior; however, significant increases in capacity were noted for high molar ratios producing a type I system.