Multiscale modeling and liquid-liquid equilibria insights for the extraction of heterocyclic nitrogen compounds from coal tar via [emim][TOS] as extractant

Abstract

Considering the types and contents of compounds rich in coal tar, it is necessary to separate and utilize the high value-added components enriched therein. And most of them could not be substituted by the petroleum industry. Pyrrole and indole are selected as the target typical heterocyclic nitrogen compounds (N-compounds) in the present work, and then, the ionic liquid extractant, 1-ethyl-3-methylimidazolium tosylate, [emim][TOS], is adopted to separate those N-compounds from coal tar. In order to confirm the intermolecular interactions and separation capacities, the multiscale analysis is performed on the extraction process. For instance, the hydrogen bond donor and accepter relationship between the ionic liquid and N-compounds are analyzed based on the COSMO-SAC model. Along with the bond lengths, interaction energies, and electron density analysis are calculated and used to verify the intermolecular interactions between the ionic liquid and N-compounds. Correspondingly, the phase equilibrium data for the ternary systems of methylbenzene + pyrrole/indole + [emim][TOS] are determined at T = 298.15 K under 101.3 kPa. Meanwhile, the calculated distribution ratio and selectivity also verified the quantum chemical calculation results. In addition, the NRTL and UNIQUAC activity coefficient models are adopted to correlate the experimental data, and the binary interaction parameters are regressed.