Ananalysis under closed loop operation of two thermally coupled distillation sequences for the separation of four-component mixtures was carried out and compared to the dynamic behaviour of a distillation sequence based on conventional columns. Responses to changes in set point for product compositions and to disturbances in feed compositions were obtained for operations with single closed loops and with four closed loops. The results indicate that the thermally coupled distillation systems are controllable, and that they may even show better dynamic responses than the conventional distillation sequence.