Introduction to Distillation
Distillation is a separation technology carried out under high vacuum conditions. It has the characteristics of low distillation temperature, high system vacuum, short heating time of materials, and high degree of separation. It is suitable for the separation of high boiling point, heat sensitive and easily oxidized substances. It has been widely used in the extraction of vitamins and active ingredients of Chinese herbal medicine in the pharmaceutical industry, petrochemical industry, food industry, cosmetics industry, agriculture and so on.
What are the Differences between Molecular Distillation and Fractional Distillation?
Fractional distillation is a separation method that separates different substances with different boiling points from the mixtures by heating the mixtures. Molecular distillation is a liquid-liquid separation method that separates different molecules with different weights. The differences between molecular distillation and fractional distillation are as follows:
1. Fractional distillation separates substances according to their different boiling points. However, molecular distillation separates substances according to their different weights.
2. Fractional distillation separates every individual substance out of mixture. However, molecular distillation can only separate some substances within the mixture out.
Difference between Short Path Distillation and Molecular Distillation
1. Different applications. Molecular distillation is used in the separation of the light molecules within the heat sensitive substances, the removal of heavy materials and colors, and so on. Short path distillation is used in the production of lactic acid, paraffin wax, monoglycerides, omega‐3 fatty acids, and monomers.
2. Different structures and scales. Compared with molecular distillation, short path distillation has a simpler structure and a smaller scale. Molecular distillation has a more complicated structure with scrapers.
3. Different working process. In the molecular distillation equipment, materials need to be added from the top and then be heated with scrapers dividing materials into a film evenly. Then the evaporated materials will be divided into heavy molecules and light molecules, which will go to different ways to be collected. In the short path distillation equipment, the materials will be heated and evaporated, then the gas-phase product will be condensed into liquid-phase and transferred into the receiving flask for users to get easily. Compared with molecular distillation, short path distillation has a simpler working process.
What are the Types of Distillation?
The distillation method is widely used in many fields, for example, chemical labs, industrial factories, food-making field, pharmaceutical field and other fields. In distillation method, there are so many types of distillation. They are as follows:
1. Fractional distillation. When the boiling points of substances within the mixture are really close, we usually use fractional distillation to separate them.
2. Simple distillation. This distillation method can save much energy, however, it has a lower distilling efficiency than other advanced distillation method.
3. Vacuum distillation. We all know that the boiling point of a liquid falls when the pressure is reduced. So in this distillation method, much heating energy can be saved because of the high pressure.
Short Path Distillation and Molecular Distillation
Short path distillation and molecular distillation are quite similar. Short path distillation is a separation method that works through a short distance under reduced pressure. Molecular distillation is a more complicated separation method than simple and traditional separation methods. There are still some differences between them.
Summary
Molecular distillation differs from traditional distillation by the principle of difference in boiling point separation. Molecular distillation achieves separation by the difference in the average free path of the molecular motion of different substances. Short-path distillation is a relatively new liquid-liquid separation technology that has not been widely used in industrial production. It can solve a large number of problems that conventional distillation techniques cannot.
