Low-level thermal energy is upgraded by using the reversible reactions of 2-propanol dehydrogenation and acetone hydrogenation. A new design criterion for optimal operation is proposed using modeling and numerical simulation. Optimal values have been obtained for the reflux ratio and the number of trays of the distillation column for given operating conditions. Simulation results show that the enthalpy efficiency is affected by the reflux ratio, feed positions into the distillation column and reaction temperatures.