Acetone with methanol form a minimum boiling point azeotrope. To separate the mixture components, extractive distillation in the presence of new ionic liquid, 1-allyl-3-methylimidazolium chloride ([Amim]Cl), was assumed. The aim of the present study was the design of an extractive distillation column (number of theoretical stages, position of input stages, reflux ratio) in which acetone with the purity of 99.5 mole % is obtained at the minimum heat duty of the column reboiler. Higher acetone–methanol separation efficiency of [Amim]Cl in comparison with e.g. 1-ethyl-3-methylimidazolium trifluoromethanesulfonate [Emim][triflate] IL was reflected in the resulting parameters of the optimised extractive distillation column: for solvent to feed ratio of 0.42, the number of theoretical stages of the extractive distillation column was 13 and the reflux ratio was 0.1. Heat demand in the reboiler of the extractive distillation column was about four times lower than that in the extractive distillation column employing [Emim][triflate] solvent. Based on the obtained results, [Amim]Cl seems to be a very good solvent for the acetone–methanol azeotropic mixture separation.