Esterification of decanoic acid during supercritical fluid extraction employing either methanol-modified carbon dioxide or a methanol trap

The methylation of decanoic acid during the supercritical fluid extraction process was investigated. It was found that the majority of the methylation occurred not during the extraction, but during the collection step, in the presence of methanol. Increasing dynamic extraction time (and hence collec tion time) from 0 to 60 min increased acid to ester conversions from 2% to 4%. The addition of HCl as a catalyst to the reaction increased the reactio n rate 10-fold, and resulted in 88% conversion to the methyl ester within 3 0 min, without any detrimental effects on the chromatographic system. Highe r collection temperatures appeared to increase conversion, but decreased me thyl ester collection efficiency. (C) 1999 Published by Elsevier Science B. V. All rights reserved.