Application of metal triflate catalysts for the trans‐esterification of Jatropha curcas L. oil with methanol and higher alcohols

Abstract

AbstractThis paper describes an experimental study on the application of metal triflate salts for the (trans‐) esterification of fatty esters (triolein, methyl oleate, methyl linoleate), fatty acid (oleic acid), as well as Jatropha curcas L. oil with methanol and higher alcohols (ethanol, n‐propanol, iso‐propanol, iso‐butanol, tert‐butanol). The effect of the metal type (scandium, bismuth, aluminium, lanthanum, copper, zinc) and process conditions on reaction performance were evaluated. Highest conversions were obtained with Al(OTf)3. Reaction of triolein with methanol gave 99 mol% conversion at 165 °C for 1 h and the main product was the methyl ester. In addition, partial methoxylation of the carbon–carbon double bonds in the fatty acid chains was observed, though their fraction in the mixture was less than 20 mol%. The trans‐esterification reaction was also successfully performed using higher alcohols, giving >95 % conversions for ethanol, n‐propanol, iso‐propanol and iso‐butanol, whereas tert‐butanol was not reactive. For the reaction of oleic acid with methanol, quantitative esterification, partial methoxylation of the carbon–carbon double bonds and the formation of small amounts of a lactone was observed. The methodology using Al(OTf)3 was successfully performed on the trans‐esterification reaction of JO (FFA content of 2.1 wt%) with various alcohols. Key properties (viscosity, pour point and cloud points) of the (branched) Jatropha esters were determined. The best cold‐flow properties were obtained for the iso‐propyl esters of JO, with cloud point and pour point of −3 and −24 °C, respectively.