The Separation Efficiency of the Molecular Distillation

Abstract

Under idealized conditions, the relative volatility of the molecular distillation of a binary mixture is higher than that of equilibrium distillation by a factor of (M2/M1)1/2, where M2 and M1 are the molecular weights of the less and more volatile components, respectively. But in practice, this advantage of molecular distillation is usually not observed experimentally. This deficiency of separation efficiency of molecular distillation is now explained by computing the effects of surface cooling, surface depletion of the more volatile component, and the nonideality of the liquid mixtures. It is noted that shorter exposure time of the liquid surface is desirable for the design of an efficient molecular still. For the estimation of the separation efficiency of molecular stills whose exposure time of the liquid surface is not controlled mechanically, the surface renewal model is considered to be more realistic.