Research On Purification Of Unsaturated Fatty Acids By Urea Inclusion Fractionation

In this study, separation and purification of linoleic acid (LA) from sunflower seed oil as raw material by urea inclusion fractionation was studied. The results indicate that in the separation of oleic acid and linoleic acid, linoleic acid of high purity can be obtained. The research results are valuable for the deep processing of sunflower oil and the development of polyunsaturated fatty acids series for the manufacturing.A fast and accurate analysis of the content of fatty acids with gas chromatography method was established, and the physiochemical properties of sunflower seed oil and its fatty acid were analyzed. The methods and the preliminary data support the research on saponification of unsaturated fatty acids and the enrichment of LA.The factors that affect the processes of the saponification and hydrolysis reaction of sunflower seed oil, including the amount of KOH, reaction temperature, reaction time and acid concentration were discussed. The results show that alkali usage and reaction time in the process of saponification reaction are the dominant factors. The optimum results showed that the highest conversion of free fatty acids is 86.2% and the recovery of LA is 93.6% in the conditions of the alcohol-to-oil ratio (v/w) of 2:1, KOH saponification equivalent amount of 1.1times, and 80±2℃water bath reaction refluxing 1.5 hour.Then, we developed a new technology for the purification of linoleic acid by urea adduction fractionation, investigated the factors in process of urea inclusion, and preliminary discussed separation mechanism of urea inclusion process. The results indicate that urea consumption is the key element that can affect the yield and purity of the product. After the first enrichment, the content of LA increased from 61.4% to 90%, and the highest purity was 98.2%. The results confirm that the inclusion process of fatty acid and urea is essentially a reactive crystallization process. Under different conditions, the crystallization process of fatty acids is speed control and balance control, respectively.Crystallization reaction conditions of urea inclusion were optimized using the response surface method, and the optimal model was developed. Using the linear weighting method of fitting model for optimization, the optimal balance between the content and the recovery of LA is obtained. Under the optimal conditions, the content of LA is 83.0%, and the recovery is 80.4% at a urea-to-fatty acids ratio (w/w) of 1.53, 95% ethanol-to-urea (v/w) of 5.00, crystallization temperature of 20℃, and crystallization time of 17h. The good agreement of the large experimental values and predictive values indicates that the crystallization system and the model have a potential to be applied in industries.