Triglyceride transesterification conditions
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This post was last edited by Standing in the East on 2011-10-28 at 15:16. To analyze the components of fish oil, esterification is necessary; however, in a base-catalyzed transesterification reaction, how can it be ensured that it is triglycerides and ethanol that undergo esterification, rather than the triglycerides being saponified by the base? After the reaction was complete, no layering was observed. When water was added, the water layer turned milky white or light yellow and appeared homogeneous, as if it had been emulsified. What could be the reason for this?
After transesterification, glycerol and fatty acid ethyl esters are produced; glycerol is soluble in water, whereas fatty acid ethyl esters are not, and adding water will definitely cause emulsification. Water cannot be added during the reaction or after it is complete. Otherwise, emulsification will occur.
Reply to 2# luberdi: How can excess catalyst be removed without adding water? . . Moreover, no layering was observed after the reaction, and it was not possible to distinguish glycerol. . . When water is added, stratification occurs; the water layer just turns milky white and remains very uniform. Isn’t glycerin colorless when dissolved in water?
This post was last edited by Standing in the East on 2011-10-26 09:26. If your fish oil is refined oil, a clear separation should occur after the reaction is complete. Without layering, the reaction essentially does not take place; whereas adding water causes emulsification, resulting in a milky white color, as soap must be present in it.
This post was last edited and replied to by tomato886 on 2011-10-25 at 16:17. Reply 4# synsj: It’s not refined fish oil; it’s crude fish oil. Before transesterification, pre-esterification is carried out using sulfuric acid to remove free fatty acids. Since the acid value is around 10, how can the reaction conditions be controlled to enable esterification to take place? If the reaction is complete, will the ethyl ester and glycerol separate immediately? Then in which layer is the remaining ethanol? Thank you
With coarse-haired oil, it’s very difficult to carry out transesterification.
Use anhydrous ethanol for ethanol; never use 95% ethanol! Saturated salt water for washing.
Reply to 6# synsj: Then what should I do to test the ingredients of crude fish oil? . .
Following the route of esterification to determine ethyl esters is likely to be quite difficult; it is recommended to adopt the approach of saponification followed by acidification, and then testing for fatty acids. Although this is not a standard method, it is relatively practical for crude oils with high acid values.
Following the route of esterification to determine ethyl esters is likely to be quite difficult; it is recommended to adopt the approach of saponification followed by acidification, and then testing for fatty acids. Although this is not a standard method, it is relatively practical for crude oils with high acid values.
Reply to 10# synsj: Thank you very much for your reply, but I still have one question I haven’t understood. Since both alkaline-catalyzed transesterification and saponification involve the reaction of fats and oils with KOH and alcohols, how can the conditions be controlled so that only transesterification or saponification occurs? What is the boundary between the reaction conditions of the two? My fish oil has an acid value of around 10; is it possible to first carry out pre-esterification using sulfuric acid as a catalyst and then ester exchange using an alkali catalyst?