| Abstract | The influence of acid/polyol molar ratio and reaction time on lipase-catalyzed esterification of oleic acid (OA) and sorbitol was studied to determine optimal conditions for monoester synthesis. A simple mathematical model was developed to determine relationships between various parameters of technical and/or economical importance. A direct relationship. independent of OA initial concentration and reaction time, was shown between the percentage of monoester in total esters, monoester concentration (the maximum was 25–30 mM for 70–80% monoester), and sorbitol conversion rate. A high sorbitol conversion was always associated with a low percentage of monoester in total ester. No absolute optimum could be found, so that compromises should be chosen, with the help of the results presented herein, depending on the constraints on the process. Two possible optima are proposed. In both examples, monoester (25–30 mM) is 80% pure. In the first case, productivity is maximized (15 mmolL−1h−1), but OA and sorbitol conversions are only 40 and 60%, respectively. In the second case, a high OA conversion (>99%) is favored at the expense of monoester productivity (1.8 mmolL−1h−1), 60% of the sorbitol being converted. It was shown that, although sorbitol monoester has better surface properties than diester, the addition of 20% diester did not modify the interfacial activity of monoester and slightly increased its surface activity. |
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