Views: 12 Author: Site Editor Publish Time: 2021-09-30 Origin: Site
It can be known from the principle of molecular distillation that it is a continuous and irreversible distillation process under high vacuum. This feature determines that it has significant advantages compared to conventional distillation.
1. Low separation temperature
Ordinary distillation needs to be carried out at the boiling point temperature of the material, and molecular distillation is based on the different properties of the mean free path after different kinds of molecules escape the liquid surface to achieve separation. Therefore, molecular distillation can be carried out below the boiling point of the material. This is the difference between molecular distillation and molecular distillation. The essential difference of conventional distillation is that the separated materials can be separated as long as there is a temperature difference. Since the separation temperature is much lower than the boiling point of the material, molecular distillation can effectively prevent the material to be separated from being decomposed by heat, and has high efficiency.
2. Low distillation pressure and high vacuum
Due to the special structure of molecular distillation equipment, the vacuum in the system is relatively high, and the pressure is less than 1Pa. According to the Claberon equation, the pressure reduction further reduces the distillation temperature, which can effectively avoid the oxidation and decomposition of easily oxidizable substances. In addition, for the removal of low-molecular substances (such as organic solvents, odor substances, etc.) in the mixed liquid, molecular distillation is much more effective than conventional distillation.
Ordinary vacuum distillation is generally several hundred to over kilopascals, which is not conducive to lowering the distillation temperature. It can be seen from the free path formula of molecular motion that, in order to obtain a sufficiently large mean free path, it can be obtained by reducing the distillation pressure P, which is generally of the order of 10-1Pa.
3. Short heating time
The distance between the heating surface and the condensation surface of the molecular distillation device is less than the mean free path of light molecules. The light molecules escaping from the liquid surface almost reach the condensation surface without collision, so the heating time is very short. In addition, the thickness of the liquid film of the material is about 0.25~0.5mm, so that the area of the liquid surface and the heating surface are almost equal, so that the heating time of the material in the distillation process becomes shorter, usually from a few seconds to tens of seconds. It protects the color and natural quality of the material well. Due to the low molecular distillation temperature and short heating time, it is very suitable for effective separation of high boiling point, heat sensitive, and easy-to-oxidize materials.
4, high degree of separation
The components have higher relative volatility than conventional distillation under molecular distillation conditions. Therefore, molecular distillation can separate components that cannot be separated by conventional evaporation and distillation. For components that can be separated by conventional distillation, molecular distillation has a higher relative volatility. efficient. Molecular distillation is often used to separate liquid mixtures that are difficult to achieve by conventional distillation.
Ordinary distillation is a reversible process of evaporation and condensation. The liquid phase and the gas phase can form a mutual equilibrium state. In the molecular distillation process, the molecules that escape from the evaporation surface directly fly to the condensation surface. In theory, this process does not collide with other molecules, and there is no possibility of returning to the evaporation surface, so molecular distillation is irreversible.
6, no boiling bubbling phenomenon
Ordinary distillation has the phenomenon of bubbling and boiling, while molecular distillation is free evaporation on the surface of the liquid layer, which is carried out at low pressure, and there is no dissolved air in the liquid. Therefore, in the molecular distillation process, the entire liquid does not boil, and no bubbling occurs.
7. Clean process and environmental protection
Molecular distillation is a purely physical separation process, non-toxic, harmless, and no residual pollution. It is a green and environmentally friendly production process, which can obtain pure and safe products, and can guarantee the natural quality of the extract, which is worthy of promotion. Promotion. At the same time, molecular distillation has a simple operation process and few equipment. It is precisely because of the many advantages of molecular distillation that it is widely used in the separation and purification of food and drug mixtures. In addition, it is also used in many fields such as the purification and separation of food additives, petroleum, oils, natural vitamins and natural pigments, and many of them have been used. Realize industrialization.