In this paper, design and optimization procedures are developed for a conventional extractive distillation sequence and a thermally coupled extractive distillation scheme. The proposed methodologies detect the optimal values of the design variables in order to guarantee the minimum energy consumption. It was found that the optimum energy consumption can be related to the minimum total annual operating cost, minimum greenhouse gas emissions, higher thermodynamic efficiencies and good theoretical control properties. The methodologies were applied to the study of the separation of close boiling point mixtures and azeotropic mixtures using the two distillation sequences. Regarding energy consumption, total annual cost, thermodynamic efficiency, greenhouse gas emissions and theoretical control properties, the thermally coupled extractive distillation sequence outperformed the conventional extractive distillation sequence. The results showed that the energy savings predicted in the complex extractive distillation sequence can be achieved along with good operational properties and reductions in greenhouse gas emissions. (C) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.