Entrainer selection using the Infinitely Sharp Split method and thermodynamic criteria for separating binary minimum-boiling azeotrope by extractive distillation

Entrainer selection for extractive distillation remains a challenge because established criteria are based on thermodynamic properties at entrainer infinite dilution, primarily developed for an extractive column. However, a cost-effective extractive distillation continuous process uses two connected - extractive and entrainer regeneration - distillation columns. Using only the ternary mixture A-B-E vapor-liquid equilibrium data, the Infinitely Sharp Split (ISS) method is combined with the driving force concept as a new thermodynamic criterion, to compare the performance of entrainers for extractive distillation process. The ISS method allows fast computation of the minimum value of both the entrainer flowrate and the reflux ratio for the extractive distillation column, while the driving force concept is related to the regeneration column design. The methodology is applied to the separation of the minimum-boiling azeotrope methanol – dimethyl carbonate with a list of five high boiling entrainers, giving methanol as distillation product of the extractive distillation column. The entrainer ranking proposed by the combined criterion agrees with optimization results of the two-column extractive distillation process. The best candidate, methyl salicylate, having the lowest minimum entrainer flow rate and reflux ratio, provides also the most cost-effective extractive distillation process.