Application of a heat pump system (HP) is a possibility for decreasing the energy demand of distillation. The separation of a low relative volatility mixture (n-heptane - toluene) by batch distillation with vapour compression (BD-VC) is investigated. The working fluids (WFs) studied are n-pentane, n-hexane and methanol, ethanol, iso-propanol. The column equipped with standard reactor-reboiler is simulated in a rigorous way (including the conditions of heat transfer). The influence of the main operational parameters and of the selection of the WF on the effectiveness (cost saving, COP, payback time) of the process is investigated.