Molecular distillation is a distillation process done under high vacuum. The very short distance the vapor travels before condensing ensures minimal to no loss due to surface hold-up of the vapor and is an immediate release from vapor to condenser surface. This distillation process is classified as short path distillation and is also referred to as molecular distillation due to the minimal vapor/liquid interface. The technique and equipment are typically used to purify substances with low volatility and/or temperature sensitivity.
Application of Molecular Distillation
Molecular distillation can be widely applied to various aspects of the national economy,especially suitable for the separation of high boiling point,heat sensitive and easily oxidized materials,such as separation and purification of fatty acids; distillation separation of natural and synthetic paraffin products; separation purification Jiao Shawan cod liver oil (ene); production of high concentration of monoglyceride;monomer MDI,TDI and two yuan of fatty acid separation polyurethane material;extraction of natural products VE;free fatty acid separation of oil products in special silicone oil; purification; separation of a small amount of solvent in natural extracts;application in polymer manufacturing; alkylpolyglucosides carotene purification;solation and purification;separation of hydrocarbons in petrochemical industry, purification of organic intermediates,antioxidant, lecithin;plastics industry by purification of plasticizer;refined emulsifier in food industry and purification of functional oil refining industry of traditional Chinese medicine;pharmaceutical intermediates;natural essential oil in the perfume industry decolorization,deodorization,improve purity etc..The summer and the purpose of the summer to give some practical examples to illustrate.
1.Single Lipid
Monoglyceride is widely used in the food industry emulsifier and proper molecular distillation technology is a typical example of that process study reported a lot, the whole process research, also has simple molecular distillation process research (Azelag and Zwierzykowski 1983). The most common method of manufacture is hardening oleic oil solution generation of so-called low content of products containing 40-50% monoglyceride and 7% glycerol and 35% diglyceride, and the rest of the unreacted triglyceride, through molecular distillation purification after, monoglyceride content in more than 90% and by-product glycerol and triglycerides can reuse, the result is almost all of the triglyceride into monoglyceride.
2.Vitamin E
Molecular distillation can be used for the production of synthetic vitamin E and natural vitamin E, the final step in the synthesis of vitamin E is in the form of acetate, containing 10% low boiling point by-products and approximately 2% resinous residue, after two stage molecular distillation, pale yellow, oily vitamin E products.Natural vitamin e found in vegetable oils in the removal of odor process as part of the fatty acids are presented, together, enriched in deodorizer distillate were, the concentration can reach more than 1%, by molecular distillation can be concentrated to 50%, even more than 70%.
3.Carotene
Carotene is a kind of vitamin, as a kind of additives widely used in food, now more and more to the use of natural carotene instead of synthetic carotene, commonly used concentration is more than 25%.To from the red palm oil (carotene content of 0.07%) for the extraction of carotenoids and general machining process is palm oil after methyl esterification by molecular distillation steam to methyl, whole process needs three-step molecular distillation, products containing carotene can reach 40%.
4.ω-3 Fatty Acid Ester in Fish Oil
Due to the fish oil containing ω-3 fatty acid glycerol ester, so eat more fish on the heart is good, but due to the constraints, the risk of heart disease is difficult to directly obtain fish nutrition, food containing high concentration of the fatty acid ester capsule is a effective method.Because of the good effect of EPA and DHA containing 5-6 double bond, high temperature and easy polymerization and failure.
5.Amide
The fatty acid amide, such as 16~20 carbon atoms,is commonly used as the emulsifier and dispersant in the textile industry,and the corresponding acid and amine reactions are derived from the reaction.Although the high product quality index (especially the chrominance) requirements, but low yield, such as quality of 98.5%, rate of not more than 88%, and the use of molecular distillation rate is up to 94%, can reduce 50% of the waste.
6. Two Polylactic Acid
Two polylactic acid is the basic raw materials of polyester,the reaction mixture containing single acid, two – acid and oligomer, need to be further refined to meet certain requirements of the product. According to reports, the current domestic and international production are used the method of molecular distillation, the Xing Ming Yang (Yang, Guo Helu, 1993) of dimer acid molecular distillation process research, Guangzhou light industry research also of dimer acid molecular distillation process were a large number of studies, scale from small test, try to 1000 tons / year industrial trial production run, with satisfactory results, can be more than 95%, light yellow color, consistent with the theoretical value of dimer acid, reaching the quality standard of similar products abroad.
7.Alkylpolyglycosides(APG)
Glucose and C8~12 fatty alcohol under catalytic conditions was obtained by the reaction of alkyl polyglycosides, obtained after the reaction is a mixture mainly not reaction of sugar, alcohol, single Chungan, glycol glycoside, multi alcohol glycosides and other product requirements single glycosides, glycosides, glycosides to maintain a certain proportion, does not contain sugar and alcohol. Therefore, it is necessary to refined, using conventional distillation may make the product deterioration of. Distillation kettle bottom coking and four molecular distillation can get qualified products, reach the level of foreign products of the same quality.
8.Purification of Capsanthin
Capsicum red pigment containing 1% to 2% of the solvent, after two stage molecular distillation processing, products dissolved residual amount < 2.0 * 10-6, meet the quality requirements (Erdweg, 1983); in addition,also can realize the effective separation of capsaicin and pigment,containing capsaicin 10% general pepper supercritical extract, by molecular distillation treatment, allicin content can rise to 25% or more.
9.Purification of Natural Essential Oil
Strong spices like volatile substances, high heat sensitivity and its common process is deodorization, decolorization and purification, generally using the three-step molecular distillation, first grade deoxidation, second level off odor or purification, the third stage bleaching or purification. Such as rose oil after molecular distillation, can solve the smell is not good, color depth and wax content of higher, so that the added value greatly improved.
Above is a typical example of the application of molecular distillation, in addition, but also can be used in many fields, such as asphalt manufacturing, silicon oil reuse, high carbon alcohol refining, sucrose ester preparation, synthetic fragrances of refining. The molecular distillation applied research laboratories were a large number of experiments and have rich experience and fruitful results, at present in mainland China has 1000 tons / year of erucic acid amide, 1500 tons / year of dimer acid, 3000 tons / year single glucoside ester, 500 tons / year of alkyl polyglycosides etc. dozens of sets of equipment in operation, with great economic benefits.
