A Hierarchical Hybrid Method for Screening Ionic Liquid Solvents for Extractions Exemplified by the Extractive Desulfurization Process

Daili Peng,Jozef G. M. Winkelman,Francesco Picchioni,Anne-Jan Kleiweg,Zhen Song

doi:10.1021/acssuschemeng.0c07866

Abstract

A hierarchical hybrid method combining experimental-database-derived estimation of extraction performance, quantitative structure–property relationship (QSPR)-based assessment of IL physical and environmental properties, liquid–liquid extraction (LLE) measurement, and process evaluation is proposed to screen practically suitable ionic liquid (IL) solvents for different extractions. From the literature, 47 424 infinite dilution activity coefficient (IDAC) data including 12 IL families (e.g., imidazolium, pyridinium, ammonium, etc.) and 13 organic families (e.g., alkanes, aromatics, alcohols, etc.) are collected. On the basis of the IDAC data, the extraction performance of ILs for a specific separation can be estimated in terms of the distribution ratio and selectivity at infinite dilution. The ILs with potentially high extraction performance and meeting the physical and environmental properties criteria are selected to perform LLE experiments. Subsequently, process simulation and evaluation using the selected IL solvents are performed by Aspen Plus. To exemplify the proposed method, the extractive desulfurization (EDS) process is taken as a case study, where [EMIM][MESO₃] (1-ethyl-3-methylimidazolium methanesulfonate) and [EIM][NO₃] (1-ethylimidazolium nitrate) are selected after IDAC database searching and QSPR analysis. Experimental LLE with the two ILs are determined, demonstrating their promising extraction performance with the maximum selectivity (S₂₃ᵐᵃˣ) for thiophene/heptane of 420 and 281.9, respectively. By fitting the NRTL model correspondingly, two processes using the screened ILs and sulfolane are developed and compared using Aspen Plus. It turns out that the two ILs save 66% and 48% in solvent requirements and 54% and 55% in energy consumption compared to those of sulfolane for the EDS task, respectively.

Highlights

In the extraction process, ionic liquid (IL) have been applied in many different areas, e.g., separation of aromatic and aliphatic hydrocarbons,[11−13] purification of drugs and biomolecules,[14,15] and desulfurization and denitrogenation of fuel oils.[16−19] Compared to traditional organic solvents, IL solvents have a negligible vapor pressure that makes them unlikely to evaporate to the environment to cause pollution and solvent loss as well as ease solvent regeneration.[20]
Because the distribution coefficient is always inversely related to the selectivity, the overall performance of solvents could be evaluated by the performance index (PI∞), which is the product of the selectivity and the distribution coefficient at infinite dilution
ILs with potentially high performance and meeting constraints of the considered properties are selected as promising candidates

Summary

■ INTRODUCTION

Due to their favorable thermophysical properties, ionic liquids (ILs) are widely regarded as promising solvents in various separation processes, such as gas capture,[1−5] extraction,[6−8] and extractive distillation.[9,10] Especially in the extraction process, ILs have been applied in many different areas, e.g., separation of aromatic and aliphatic hydrocarbons,[11−13] purification of drugs and biomolecules,[14,15] and desulfurization and denitrogenation of fuel oils.[16−19] Compared to traditional organic solvents, IL solvents have a negligible vapor pressure that makes them unlikely to evaporate to the environment to cause pollution and solvent loss as well as ease solvent regeneration.[20]. No ionic liquids are found in the raffinate, which is strongly favorable for the EDS process to avoid the potential contamination of fuel by the nitrogen- and/or sulfurcontaining ILs.[78,79] the concentrations of alkanes in all the extract phase are at a magnitude of 10−3, which correspond to the high extraction selectivity of the ILs. The results for the Hand and Othmer−Tobias consistency tests are listed in Table S6 (Supporting Information). [EMIM][MESO3] is better than [EIM][NO3] since the EDS process using [EMIM][MESO3] needs a similar amount of heat duty and much less solvent compared to that of [EIM][NO3]

■ CONCLUSIONS

Results

■ ACKNOWLEDGMENTS

■ REFERENCES