Application of Molecular Distillation Technology in Vitamin Extraction

Vitamins are products that are closely related to people's lives, and have become one of the main bulk products in the international pharmaceutical and health care products market. The amount of vitamin E is the largest, followed by vitamin A, vitamin C, vitamin D and so on. With the growth of economy and the improvement of people's living standards, the demand for vitamin products will further increase, and people's requirements for their quality and grade will also further increase. Therefore, as an important separation technology in the production of many vitamins, molecular Distillation technology will also play an increasingly important role in the vitamin industry.

1. The basic principle of molecular distillation technology

   Molecular distillation is different from general distillation techniques. It uses the difference in the mean free path of molecular motion of different substances to achieve the separation of substances, so it can be operated far away from the boiling point.

   According to the theory of molecular motion, the movement of the molecules of the liquid mixture will intensify after being heated. When they receive enough energy, they will escape from the liquid surface and become gas phase molecules. With the increase of the gas phase molecules above the liquid surface, some of the gas will return to the liquid. , when the external conditions remain constant, the dynamic equilibrium of molecular motion will be reached. From a macro point of view, a balance has been reached.

   In order to achieve the purpose of separation, the liquid mixture is first heated, and the molecules with sufficient energy escape the liquid surface. The mean free path of the light molecules is large, and the average free path of the heavy molecules is small. A condensation surface is set at the mean free path of the heavy molecules, so that the light molecules are continuously condensed, thus destroying the dynamic balance of the light molecules and causing the light molecules in the mixture to escape continuously, and the heavy molecules quickly tend to the condensation surface because they cannot reach the condensation surface. Due to the dynamic balance, it no longer escapes from the mixed liquid, so that the liquid mixture has achieved the purpose of separation.

2. Features of molecular distillation technology:

   From the principle of molecular distillation, it can be seen that molecular distillation has many characteristics that conventional distillation does not have.

2.1 The operating vacuum of molecular distillation is high

  Since the distance between the hot and cold surfaces of molecular distillation is smaller than the mean free path of light molecules, light molecules reach the condensation surface with almost no pressure drop, so that the actual operating vacuum of the evaporation surface is several orders of magnitude higher than that of traditional vacuum distillation. . The operating residual pressure of molecular distillation is generally on the order of 0.1~1Pa

2.2 The operating temperature of molecular distillation is low.

  Molecular distillation relies on the difference in the mean free path of molecular motion to achieve separation, and does not need to reach the boiling point of the material. In addition, the operating vacuum of molecular distillation is higher, which further reduces the operating temperature.

2.3 During the molecular distillation separation process, the material is heated for a short time.

  During the evaporation process of molecular distillation, the material is forced to form a thin liquid film and is pushed in a direction, so that the liquid stays in the separator for a short time. In particular, light molecules condense as soon as they escape, and the heating time is shorter, usually a few seconds or more than ten seconds. In this way, the heat damage to the material is very small, especially for the separation process of heat-sensitive substances, it provides operating conditions that cannot be compared with traditional distillation.

2.4 The degree of separation of molecular distillation is higher. It can be seen from the relative volatility of molecular distillation:

  ατ= p1/p2 · (M2 / M1)1/2. In the formula, M1 is the molecular weight of the light component; M2 is the molecular weight of the heavy component; p1 and p2 are the vapor pressures of components 1 and 2, respectively.

  And the relative volatility of conventional distillation, α=p1/p2. In the case of the same p1/p2, the molecular weight M2 of the heavy component is larger than the molecular weight M1 of the light component, so ατ is larger than α. This indicates that molecular distillation is easier to separate than conventional distillation, and the greater the difference between M1 and M2, the higher the degree of separation.

  It can be seen from the above characteristics that molecular distillation technology can separate substances that are difficult to separate by conventional distillation, and is especially suitable for the separation of high boiling point and heat sensitive substances. Therefore, it has broad application prospects in the vitamin industry as an effective means of purification and separation.

Example 1. Application of molecular distillation technology in vitamin industry

  At present, in the vitamin industry, there are many varieties, whether synthetic or natural, the production process requires the use of molecular distillation technology. Example 1. The application of molecular distillation technology in the production of natural vitamin E.

  Natural vitamin E widely exists in the green parts of plants and grass seed germs, especially in vegetable oils, generally at 0.05-0.5%. Since the content of sucrose does not have the economic value for extracting natural vitamin E products, natural vitamin E products cannot be directly extracted from vegetable oils as raw materials. However, in the refining process of vegetable oil degumming, deacidification, decolorization, deodorization, etc., the natural vitamin E is concentrated in the deodorization extract, generally containing 1%-15% of the mass fraction. Therefore, the oil deodorization fraction is the extraction of natural vitamin E ideal resource. my country is rich in vegetable oil resources. Extracting natural vitamin E from refined by-products is not only the comprehensive utilization of natural resources, but also the best way to obtain natural vitamin E. Good conditions are provided.

  There are many extraction techniques for natural vitamin E, such as: chemical solvent extraction, urea precipitation, vacuum distillation, multistage distillation, molecular distillation, supercritical CO, etc. But no matter what method, to produce high-quality natural vitamin E products, the most critical issue is whether the extraction and separation process is advanced, and whether the following conditions can be met:

1. Protect the natural quality of the product to the greatest extent.

2. The product must be free from chemical pollution.

3. The production process must have industrial economic value

To meet the above requirements, the simple solvent extraction method is not enough, because the solvent will remain in the product, and the traditional decompression and rectification method is not good, because the extremely high operating temperature will damage the Ve product and produce new impurities. Direct use Supercritical extraction is also uneconomical from an industrial point of view. Therefore, to meet the safety requirements of the product and have industrial value, the preferred method is molecular distillation. Taking the Ve production method developed by Xinte Company of Beijing University of Chemical Technology as an example, the extraction technology of natural vitamin E will be introduced.

The deodorized distillate generally contains 3-10% Ve, 6-10% phytosterols, about 40% free fatty acids, about 20% neutral oils, and other hydrocarbons, odorous substances and pigments.

The raw material production process can be simply expressed as:

  The purpose of methanol esterification is to convert the fatty acid and neutral oil in the raw material into fatty acid methanol. After the esterification, the mixed liquid is treated by physical methods to separate sterols and excess methanol, and then enters the molecular distillation process.

  Due to the difference in the free path of molecular motion between fatty acid formazan and natural vitamin E, molecular distillation can effectively remove fatty acid formazan in the mixture, and can realize the separation of natural Ve products from larger molecules such as neutral oils and pigments, thereby I got Ve products that maintain the characteristics of pure nature. Such products are very safe and effective.

Example 2. Application of molecular distillation technology in the production of synthetic vitamin E

  The production process of synthetic vitamin E is complicated. It uses acetone as the starting material to produce linalool through reactions such as quickening, hydrogenation, and condensation. Phytoalcohol is condensed and acidified to obtain vitamin E. In this production process, the purification of isophytol and vitamin E is suitable to be realized by molecular distillation technology. In particular, the final product vitamin E is currently refined by molecular distillation at home and abroad to ensure product quality. The capacity of a single production line of molecular distillation equipment has reached 20,000 tons per year.

Example 3. Application of molecular distillation technology in natural vitamin A extraction

  Natural vitamin A is one of the earliest varieties of industrial application of molecular distillation technology. As early as the middle of the last century, people completed the industrial production of vitamin A distilled from cod liver oil. It's just that the molecular distillation evaporator at that time was a falling film type, which was bulky and had poor separation efficiency. Even so, the role of molecular distillation technology in the purification of natural vitamin A has been regarded as a classic example of the application of molecular distillation technology. On the one hand, as natural vitamin A is a high-boiling point, heat-sensitive substance, its industrial production requires new separation technology; on the other hand, the development of molecular distillation technology needs to use typical products as a breakthrough. The organic combination of the two promotes the common progress of technology and products.

  Even with the mass production of synthetic vitamin A today, the extraction of natural vitamin A from cod liver oil is still an important source of human nutrition. Natural vitamin A extracted from cod liver oil of crocodile, fresh fish, tuna, etc. Active substances are still regarded as the safest health food and are widely used in nutritional food for infants and young children.

Example 4. Application of Molecular Distillation Technique in Vitamin D Extraction

  Vitamin D is a steroid derivative, and vitamin D (also known as activated 7-dehydrocholesterol, C27H44O) is often used as a food nutrition enhancer. In the process of preparing vitamin D3 by reacting vitamin D3 resin with amphiphile, the content of vitamin D3 can be increased by 515% by using molecular distillation technology.

Example 5. Application of molecular distillation technology in vitamin K extraction

  Vitamin K1 is 2-methyl-3-phytyl-1,4 naphthoquinone, it participates in the synthesis of thrombin and other coagulation factors in the liver, and is an important nutrient for maintaining the physiological functions of the human body. Vitamin K1 can be extracted from natural plants, but it is mainly produced by chemical synthesis. Whether it is extracted from natural products or produced by chemical synthesis, its purification process can use molecular distillation technology. The reason is that vitamin K1 has a high boiling point and strong heat sensitivity. Traditional distillation not only has a low yield, but also has poor quality. However, the use of molecular distillation technology can significantly improve the quality and yield of products. Aishengke uses molecular distillation to process crude vitamin K1 to make the product meet the requirements of pharmaceutical grade, and the product yield is as high as 85%.

  In addition, molecular distillation technology can also be widely used in the purification of many intermediate raw materials in vitamin synthesis. For example, β-ionone is an important intermediate raw material for the synthesis of vitamin A and E. It can be synthesized by extracting citral from natural litsea cubeba oil. Not only the extraction of citral can be accomplished by multi-stage molecular distillation, but also the purification of β-ionone is inseparable from molecular distillation technology.

  In conclusion, molecular distillation technology has a good application prospect in the vitamin industry. As long as we pay attention to the optimal combination of molecular distillation technology and other related technologies in practical applications, molecular distillation technology will play a greater role.

  AISHENGKE company adopts the Wiped-Film Style, which is very different from the traditional Roller Style, mainly in the scraper system. We use Smith diagonal chute scrapers which are well documented to be much more efficient than rollers. These scrapers provide a high degree of film mixing for optimum heat and mass transfer. In contrast, the rollers passively roll the material against the walls of the retort without producing effective microscopic active movement of the material. The chute on the scraper will force the material to move down around the still wall, so as to achieve the shortest and controllable material residence time, and controllable film thickness. In addition, the scraper will not throw the material off the still wall and cause pollution. However, there will be such problems during the use of the roller, just like a car tire driving on a wet road, then the liquid will definitely leave the road and splash everywhere, polluting the light components that have been separated, the separation effect and product quality will be affected. out of control.

Advantages of Aishengke Molecular Distillation
1. The distillation temperature is low. Molecular distillation operates at a temperature far below the boiling point. As long as there is a temperature difference, separation can be achieved. This is the essential difference between molecular distillation and conventional distillation.

2. The distillation has a high true value, and a high vacuum value can be obtained inside the molecular distillation device. Generally, molecular distillation is operated under very low pressure, so the material is not easily damaged by oxidation.

3. The distilled liquid film is thin and the heat transfer efficiency is high.

4. The heating time of the material is short, and the distance between the heated liquid surface and the condensation surface is smaller than the mean free path of light molecules, so the light molecules escaping from the liquid surface reach the condensation surface almost without collision. Therefore, the heating time of the distillation material is short, and the residence time at the distillation temperature is usually between a few seconds and tens of seconds, which reduces the chance of thermal decomposition of the material.

5. The degree of separation is higher, and molecular distillation can separate substances that are difficult to separate by conventional methods.

6. No boiling and bubbling. Molecular distillation is free evaporation at the surface of a liquid layer at low pressure. There are no dissolved air bodies in the liquid, so the whole liquid does not boil, nor does it bubble when distilled.

7. Non-toxic, harmless, non-polluting, non-residue, pure and safe products can be obtained, with simple operation process and less equipment. Molecular distillation technology can separate substances that are difficult to separate by conventional distillation.

8. Molecular distillation equipment is very expensive. Molecular distillation equipment must ensure that the system pressure reaches a high degree of vacuum, and has high requirements for material sealing. The distance between the evaporation surface and the condensation surface must be moderate, the processing is difficult, and the price is expensive.

9. The energy consumption of the product is small, because the superheat loss of the whole separation of molecular distillation is small, and because of the unique structure of the molecular distillation device, the internal pressure is extremely low, and the internal resistance is much smaller than that of conventional distillation, so energy consumption can be greatly saved. From the above characteristics of molecular distillation technology, in actual industrial application, it has the following obvious advantages over conventional distillation technology:

(1) Molecular distillation provides a better separation method for the separation of high boiling point, heat sensitive and easily oxidized substances. Because the molecular distillation is operated at a temperature far lower than the boiling point of the material, the residence time of the material is short;

(2) Molecular distillation can effectively remove substances in liquids, such as organic solvents and odors. This is a very effective method of desolventizing liquids after solvent extraction.

(3) Molecular distillation can selectively distill out the target product and remove other impurities, and can simultaneously separate two or more substances through multi-stage separation;

(4) The fractionation process of molecular distillation is a physical process, so the separated substances can be well protected from pollution and damage.

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