Separation of benzene and thiophene with a mixture of N-methyl-2-pyrrolidinone (NMP) and ionic liquid as the entrainer

• NMP and ionic liquid (IL) mixture were proposed for the separation of benzene and thiophene by extractive distillation.
• Isobaric VLE data were measured for benzene and thiophene system using NMP and NMP + IL mixture as entrainers.
• UNIFAC model was extended to benzene–thiophene–NMP and benzene–thiophene–NMP–IL systems.

In this study, a mixture of N-methyl-2-pyrrolidinone (NMP) and ionic liquid (IL) was proposed as the entrainer for the separation of benzene and thiophene by extractive distillation. [EMIM]+[BF4]− might be a suitable IL for investigating the selectivity and capacity together using the COSMO-RS model. The experimental vapor–liquid equilibrium (VLE) results indicated that the addition of IL did not obviously improve the relative volatility of benzene to thiophene; however, the content of NMP in the vapor phase could be significantly reduced using the combination of NMP and [EMIM]+[BF4]− in comparison to the benchmark solvent NMP. Moreover, the UNIFAC model was extended and the corresponding interaction parameters were obtained by correlating the ternary (benzene + thiophene + NMP) and quaternary (benzene + thiophene + NMP + [EMIM]+[BF4]−) VLE equilibrium data obtained in this work at ambient pressure.