Abstract
This study aimed to design a process for methylcyclohexane-toluene mixture separation. For the separation of a binary mixture containing 10 mole % of toluene, two imidazolium ionic liquids (ILs) were tested, namely 1-hexyl-3-methylimidazolium tetracyanoborate [Hmim][TCB] and 1-butyl-3-methylimidazolium tetracyanoborate [Bmim][TCB]. These ILs were chosen to substitute traditional solvents, such as N-methyl-2-pyrrolidone, sulfolane or glycols, to minimize the content of extraction solvent in the separation products and to optimize the separation process expenditures.
A separation unit composed of a counter-current extraction column, vacuum evaporator and a vacuum distillation column was suggested for the process. Prescribed efficiency of the separation units was as follows: minimum methylcyclohexane of 99.5 mole % in the raffinate phase in the extraction column, ionic liquid purity regenerated in vacuum evaporator above 99 mole %, and minimum toluene purity leaving the bottom of the vacuum distillation column of 99.5 mol%.
Simulation of the counter-current extraction column was carried out in Matlab. Operation of the remaining separation equipment was simulated using the Aspen Plus program which allowed evaluation of the energetic requirements of the proposed separation unit. It was found that both ionic liquids ([Hmim][TCB] and [Bmim][TCB]) are almost equally appropriate for this task. A comparison of energy consumption of the process using each ionic liquid was done. For [Hmim][TCB], heat integration of the separation unit was accomplished. Employing a part of the heat content of the regenerated solvent for extract stream preheating, significantly reduced unit energy consumption (by about 72 %).
