Batchwise extraction of methyl linolenate (18:3, ALA) from fatty acid methyl esters derived from soybean and canola oils using silver nitrate/silica gel

Abstract

The incipient wetness impregnation (IWI) method was used to prepare a series of AgNO3/SiO2 adsorbents that were used for the extraction of unsaturated FAMEs from hexane solutions of methyl soyate and methyl canolate. The AgNO3/SiO2‐IWI adsorbents with the highest AgNO3 loadings (40 or 50% w/w) were the most selective for the removal of methyl linolenate (18:3). For example, extractions with 40% AgNO3/SiO2‐IWI reduce the amount of 18:3 from 7.0% in methyl soyate (1.00 mL) to 1.3% while extracting only 9% of the original FAMEs mixture. The extracted FAMEs fraction has a very high 18:3 (55.6%) and 18:2 (41.9%) composition. This adsorbent maintained its selectivity for 18:3 in at least four successive extractions. Similar extractions of methyl canolate yield a biodiesel that contains much smaller amounts of 18:3. The amounts of 18:3 and 18:2 that are extracted can be controlled by the AgNO3 loading and the amount of AgNO3/SiO2‐IWI that is used.Practical applications: Results of the reported studies show that AgNO3/SiO2 is able to preferentially remove methyl linolenate (18:3, ALA) from methyl soyate and methyl canolate. This batchwise process makes these biodiesels a source of the omega‐3 fatty acid ALA and gives a biodiesel that is less sensitive to oxidative deterioration.FAMEs derived from soybean and canola oils, when treated with AgNO3/SiO2, are separated into a portion that is enriched in 18:3 (ALA) and a biodiesel that contains the more saturated FAMEs.