Study On Synthesis Techniques Of L-ascorbyl Palmitate For New Antioxidant

L-ascorbyl palmitate (L-AP or AP) is a kind of new, fat-soluble,innocuous,multi-functional nutritional antioxidant. It is an internationally accepted new foodantioxidant in recent years, and it is an exclusive antioxidant which can be allowedto apply to infant food. L-ascorbyl palmitate not only reserves the antioxygenproperty of L-ascorbic acid, but also has considerable solubility in animal andvegetable oil that can be easily digested and absorbed by human, and it can alsobring synergism with VE. In oil, L-ascorbyl palmitate has strongly antioxygenproperty and has obviously high temperature resistance.Therefore, L-ascorbylpalmitate can be applied to oil, food, medicine, health protection and cosmetics.At present, the requirement of L-ascorbyl palmitate is about 5000 ton per yearin the world. But its high cost hold up its usage. The production methods ofindustrial L-ascorbyl palmitate almost all adopts sulfuric acid direct esterification.But the method still has some problems such as difficulty of separation, low purity,high cost and so on. In the purification process, the consumption of solvent likecholoroform or aether is large and cost of it is increased so much that usuallyoccupies 30-40% that of raw stuffs, which in turn,lowers the possibility of savingbasic cost during production. Consequently, solving the problem of traditionalsynthesis techniques of L-ascorbyl palmitate and achieving the aim of low cost, highquality and easy speration are keys for spread of usage of L-ascorbyl palmitate. In this paper, we adopted the sulfric acid direct esterification method which isa method of technical maturity, high yield. In the separation process, we used blendedliquor of ice water and ethyl acetate to replace ice water as crude precipitationsolvent. In the purification process, we used the cheap toluene to replacecholoroform and aether as solvent, and use extraction method to replace washmethod, then used the blended liquor of hexane and ethanol to replace hexane torecrystallize crude products.In this paper, the effects of molar ratio of palmitic acid and L-ascorbicacid,reaction time, mass ratio of sulfric acid and L-ascorbic acid, and reactiontemperature on the yield are particularly researched. And the techniques conditionsare optimized by orthogonal experiment design. And good techniques conditions andyield are received, the molar ratio of palmitic acid and L-ascorbic acid is 1.4, themass ratio of sulfric acid and L-ascorbic acid is 12.6, the reaction temperature is30℃, the reaction time is 24h, and the yield of crude products is 83.4%0In the separation process, we have compared the effects of new precipitationsolvent and ice water on the crude products configuration and discussed the bestproportion of new precipitation solvent. This method avoided emulsification andgained better grain shape. It makes the crude products separation easily and the bestvolume proportion of ice water and ethyl acetate is 1 :(0.29-0.3).In the purification process, we researched the effects of the extractiontemperature of toluene on the recovery rate of products,and the effects of therecrystallisation temperature of the blended liquor of hexane and ethanol on the therecovery rate of products, and studied on the best proportion of blended liquor ofhexane and ethanol. The best purification conditions and recovery rate are obtained.Extraction temperature of toluene is 8℃, and the recovery rate of products is 78.7%,the best proportion of the blended liquor of hexane and ethanol is 1:0.5,recrystallisation temperature of the blended liquor is 18℃, the recovery rate ofproducts is 74.7%.In this paper, the new precipitation solvent makes the separation process easy,and the methods of extraction and recrystallisation only consume a little solvent, and the cost of solvent is only about 6.9% of the whole material cost, it is 1/5-1/6 ofthe traditional purification techniques cost. The the product cost of L-ascorbylpahnitate is estimated 83.29 yuan(RMB) per kilogram. This improved techniqueextremely cut down the cost, it has good industrial foreground. The products wastested by melting point, high performance liquid chromatography, infraredabsorption spectrum, and the results indicated the content of L-ascorbyl palmitate inthe self-made product is 98.5%, the melting piont is 108.7-115℃. The products havegood outward appearance and stable colour. The quality of products attain to thestandards of GB16314-1996 and the level of domestic similar products. All thisshow that the self-made L-ascorbyl palmitate synthesis techniques have achieved theaim of low cost, high quality and easy separation.