Molecular distillation is vacuum distillation below the pressure of 0.01 torr. It is a process of separation, purification and concentration of natural products, complex and thermally sensitive molecules for example vitamins and polyunsaturated fatty acids. This process is characterized by short term exposure of the distillate liquid to high temperatures, by high vacuum pressure (around 1024 mmHg) in the distillation column and a small distance between the evaporator and the condenser around 2 cm, where fluids are in the free molecular flow regime, i.e. the mean free path of molecules is comparable to the size of the equipment. This process has the advantages of avoiding the problem of toxicity that occurs in techniques that use solvents as the separating agent, and also of minimizing losses due to thermal decomposition.
Molecular distillation is used industrially for purification of oils.It is also used to enrich borage oil in γ-linolenic acid (GLA) and also to recover tocopherols from deodorizer distillate of soybean oil (DDSO).
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