In this work we have optimized a batch distillation column as an optimal control policy problem. We used the optimal constant reflux policy for the process, and the objective function is to maximize the thermodynamic efficiency for a fixed time given a product concentration. The simulation model of the column considers its complete dynamics, and it has been formulated as a nonlinear programming problem for the solution of the thermodynamic efficiency. We use a SQP based dynamic optimization technique in this work. The procedure is shown for the separation of a binary mixture Benzene + Toluene. The achieved accumulated thermodynamic efficiency was close to 80%. Also we have compared with the optimal control problem of the maximum distillate for the same separation above, and we can observe that in the problem we proposed, less reflux is required, and even when thermodynamic efficiency in the problems is quite close, the energetic requirement in the problem we propose herein is smaller.