Research On Synthetizing Of Linoleic Acid Ethyl Ester From Corn Oil

Linoleic acid ethyl ester is a kind of polyunsaturated fatty acid ester, with avariety of physiological activity. At present, the preparation of linoleic acid ethyleste is commonly used to put the glyceride of soybean oil or sunflower oil convertedinto linoleic acid. And sulfuric acid was used as catalyst in the esterification oflinoleic acid and ethanol. Although its high catalytic activity, cheap and abundant;but there are lots of problems such as serious equipment corrosion and environmentpollution; and linoleic acid was prone to oxidate in the esterification, unsaturateddouble bonds in molecules were destroyed and resulted in a decline in the iodinevalue of the linoleic acid ethyl ester, its quality was also difficult to meet therequirements of pharmaceutical industry. Therefore, it becomes the key point in thepreparation of linoleic acid ethyl ester that the selection of highly active, highlyselectivity and environment amity of catalyst and of simple equipment, economicaland practical of reaction process. In this paper, corn oil as raw materials is rich inlinoleic acid, the enzymatic or chemical synthesis and purification of linoleic acidethyl este was investigated, and in order to lower the cost, shorten the reaction timeand improve efficiency, and it provide ideas and theoretical basis for the preparationof linoleic acid ethyl este. Last the antioxidant properties of linoleic acid ethyl esterand selection of the optimal antioxidant were investigated.The synthesis, purification and anti-oxidation of linoleic acid ethyl ester wasstudied to Optimize process. The results show that:1. Enzymatic synthesis of fatty acid ethyl ester.（1） Based on the results of single factor analysis, optimizing the processingparameters of enzymatic synthesis of linoleic acid ethyl ester: the molar ratio ofethanol and oil4:1, the amount of enzyme30%, reaction temperature50℃andreaction time24h.（2） On the basis of single factor experiment, Optimizing the processingparameters of enzymatic synthesis of linoleic acid ethyl ester by response surfaceexperiments, and get the following regression equation:Y=90.05-0.28X₁+3.09X₂+0.68X₃+0.43X₄+1.99X₁X₂+3.41X₁X₃-1.24X₁X₄+0.44X₂X₃+1.09X₂X₃+0.33X₃X₄9.85（X₁）²-19.36（X₂）²-9.44（X₃）²-6.92（X₄）²（3） According to the regression model, the optimum conditions were as follows: the molar ratio of ethanol and oil4:1, the amount of enzyme30%, reactiontemperature50.39℃and reaction time24h, the rate of conversion of corn oil can reach90.20%under these conditions.2. Chemical synthesis of fatty acid ethyl ester.（1） Based on the results of single factor analysis, the optimum conditions were asfollows: the molar ratio of ethanol and oil8:1, the amount of KOH1.4%, reactiontemperature70℃and reaction time2h.（2） On the basis of single factor experiment, optimizing the processingparameters of chemical synthesis of linoleic acid ethyl ester by response surfaceexperiments, and get the following regression equation:Y=96.22+4.48X₁+2.74X₂+0.38X₃+1.59X₄-0.92X₁X₂-0.36X₁X₃+0.38X₁X₄-1.05X₂X₃+1.87X₂X₄+0.70X₃X₄-6.01X₁-6.35X₂-3.60X₃-3.64X₄（3） According to the regression model, the optimum conditions are as follows:the molar ratio of ethanol and oil8.36:1, the amount of KOH1.45%, reactiontemperature70.31℃and reaction time2.15h, the rate of conversion of corn oil canreach97.59%under these conditions. Compared to enzymatic synthesis of fatty acidethyl ester, as chemical synthesis have the advantages of shorten reaction time andhigh conversion rate, so this paper uses the chemical synthesis to prepare fatty acidethyl ester.3. Enrichment of linoleic acid ethyl ester through the uring bag reaction.（1） Based on the results of single factor analysis, the best process of uring bagreaction were confirming, while the recovery rate of linoleic acid ethyl ester andiodine value as evaluation index: the quality ratio of fatty acid ethyl ester and urea1:1.5, the ratio of urea quality and ethonal volume1:3.5, crystallization temperature4℃, crystallization time15h.（2） Orthogonal test show that: the effect for the uring bag reaction of linoleicacid ethyl ester was rystallization temperature> the ratio of urea quality and ethonalvolume> the quality ratio of fatty acid ethyl ester and urea. The optimum processconditions of purification of linoleic acid ethyl ester were as follows: the qualityratio of fatty acid ethyl ester and urea1:1.5, the ratio of urea quality and ethonalvolume1:3.5, crystallization temperature4℃.4. Silver silica gel column chromatography was investigated to purify linoleic acidethyl ester.（1） Different eluant systems and its composition have great effect in elutioncharacteristics of linoleic acid ethyl ester through silver silica gel column chromatography, some of its separation are good, others are bad. Petroleum ether/aether/acetic acid（8:3:0.5,v/v/v） was the optimum eluant systems by thin layerchromatography experiment.（2） The optimum process conditions were as follows by comprehensiveconsideration of tomographic results and process parameters: the packing height ofcolumn15cm, sample loading2g, the elution rate2.0mL/min; this method wassimple and could be large-scale for the purification of linoleic acid ethyl ester.5. The quality evaluation and oxidation stability of linoleic acid ethyl ester.（1） The purification of linoleic acid ethyl ester was pale yellow oily liquid, thephysical and chemical properties of linoleic acid ethyl ester meet the nationalstandards.（2） TBHQ, BHT and VE have some effect in the antioxidant stability of linoleicacid ethyl ester through Schaal oven method, the antioxidant of0.02%VE is poor,while TBHQ is the most ideal antioxidant of linoleic acid ethyl ester.（3） The effect for the antioxidant stability of linoleic acid ethyl ester was TBHQ>BHT>VE, as the higher antioxidant effect of linoleic acid ethyl ester due to thegreater amount of TBHQ, the optimun adding quality of TBHQ was0.02%quality oflinoleic acid ethyl ester.