Improved Design of Maximum-Boiling Phenol/Cyclohexanone Separation with Experimentally Verified Vapor–Liquid Equilibrium Behaviors

There are very few papers in the open literature studying the design of extractive distillation system for separating maximum-boiling mixtures. Using the knowledge of the curvature of the distillation boundary existing in such systems with a heavy entrainer, feasibility of separation can easily be determined by plotting the ternary diagram with distillation boundary and material balance lines of the studied system. In this paper, an industrially important phenol/cyclohexanone separation system is thoroughly studied to obtain an energy-efficient two-column extractive distillation process for this separation task. A heavy entrainer, triethylene glycol (TEG), is found to be an effective entrainer for the development of the proposed system. Binary and ternary vapor–liquid equilibrium experiments were conducted to obtain the binary model parameters of TEG-phenol and TEG-cyclohexanone pairs from regression. With confidence of the simulation investigations, it is found that economics of the resulting heat-integrated extractive distillation system proposed in this paper can significantly cut the total annual cost by 65.8% and also cut the total operating cost by 71.1%, as compared to that of an existing separation system in the open literature.