The production of methyl esters from vegetable oil/fatty acid mixtures

The one-phase acid- and base-catalyzed methanolysis of soybean oil and palmitic acid/soybean oil mixtures has been investigated. Methyl tert-butyl ether (MTBE) was used as cosolvent to form the single phase. A two-step method employing acid and base catalysis sequentially has been developed for producing methyl ester from oils which have significant fatty acid content.; One-phase methanolysis of pure soybean oil at room temperature using 1.0 wt.% sodium hydroxide (27:1 methanol/oil molar ratio) resulted in a 99.6% methyl ester content of the product in only 8 minutes. In contrast, one-phase methanolysis of soybean oil (30:1 methanol/oil molar ratio) with 2.0 wt.% concentrated sulfuric acid at 57°C resulted in a 96.6% methyl ester content of the product in 10 hours. In addition, one-phase acid catalyzed methanolysis of soybean oil/palmitic acid mixtures of different compositions produced a maximum 97.5% methyl ester content of the product in 10 hours. One-phase methanolysis of pure palmitic acid yielded product containing 99.8% ester after 10 hours; more importantly only 1.4 % of palmitic: acid was unreacted after 33 minutes*.; A two-step methanolysis batch process in which an acid-catalyzed step was followed by a base-catalyzed step, converted a 50/50 by weight palmitic acid/soybean oil mixture to a 95.1% yield of 99.9% purity product in approximately 3.5 hours.; *Dr. Samir Konar—private communication.