Molecular Distillation

Abstract

In this work, important results from simulations are presented, showing the potentiality of the molecular distillation process for recovering vitamin E from vegetal oils. Two types of molecular distillators are considered: falling film and centrifugal. The results emphasize the degree of recovery and factors that influence substantially the performance of the molecular distillators, such as feed flow rate, residence time, and process temperature. Moreover, they show that each type of molecular distillator enables one to operate under specific residence time and temperature. Therefore, a careful analysis must be made in order to determine the best equipment and operating conditions for obtaining products with high quality and concentration, and reduced problems of material thermal decomposition. Vitamin E (tocopherols) from vegetal oils, more specifically, from the deodorizer distillate of soya oil, was the studied case.

Separating Tocotrienols from Palm Oil by Molecular Distillation

“…(32) When PFAD is used directly in the molecular distillation process, it would not be efficient to obtain a product with high tocotrienol and tocopherol concentration, as was the result from the process using deodorizer distillate of soya oil. (8) Conventionally preparing high-purity concentrate of tocotrienols and tocopherols normally involves a series of physical and chemical treatment steps. The process requires a pretreatment to transform heavier components into components of small molecular weights.…”

“…Fat soluble 6-hydroxychroman compounds exhibit biological activity, (8,10) and can be divided into two subgroups, tocopherols and tocotrienols (Fig. 1).…”

“…(10) The antioxidant activity of 1 mg of all-rac-α-tocopheryl acetate equals the activity of 0.67 mg of d-α-tocopherol. (8,16) Table 2 shows the biological activities of some tocopherols and tocotrienols relative to natural d-α-tocopherol as assayed by the rat resorption-gestation test. (10) d-α-tocopherol has the highest antioxidant activity, while d-α-tocotrienol manifest only about 30% of this activity.…”

Evaluation of Tocopherol Recovery Through Simulation of Molecular Distillation Process

“…4). Several systems were studied by these investigators, and an average error of about 10% was noted: (4) in which D~R is the mutual diffusion coefficient of solute A at very low concentrations in solvent B (cm 2 Is); MB is the molecular weight of solvent B (g/mol); T is the temperature (K); 11B is the viscosity of solvent B (cP); VbA is the molar volume of solute A at its normal boiling temperature (cm 3 /mol), and <1> is the association factor of solvent B (dimensionless). Wilke and Chang recommend that <1> be chosen as 2.6 if the solvent is water, 1.9 if it is methanol, 1.5 if it is ethanol, and 1.0 if it is unassociated.…”

“…By reducing the pressure of non condensable gas in the evaporator to lower than 10-1 mbar, a reduction in distillation temperature can be obtained. A molecular distillation process is useful in the separation and purification of materials of high molecular weight, as well as for those that are thermally sensitive, such as the vitamins (2)(3)(4), by minimizing losses through thermal decomposition. The combination of a small distance between the evaporator and the condenser (about 2 cm) and a high vacuum in the distillation gap results in a specific mass transfer mechanism with evaporation outputs as high as 20-40 g/(m-2 ·s).…”