Operational parameters for ethyl ester production from palm olein using a strong anion exchange resin

Ethyl esters are widely used in the food industry as a thickening, plasticizer and emulsifying agent. Ethyl esters are obtained mainly by transesterification reaction of vegetable oils with short chain alcohols in the presence of homogeneous or heterogeneous catalysts. Alkaline homogeneous catalysis is the most often used technique. Nevertheless, unlike homogeneous catalysis, heterogeneous catalysts do not generate soaps, enable simpler product and catalyst separation, decreasing the need for downstream purification, and allow waste treatment in a more environmentally friendly way.
Therefore, the aim for this work was the evaluation of the commercial resin Amberlyst A26OH, a strong anion exchange resin, as heterogeneous catalyst for the batch transesterification of refined palm olein with ethanol. In the present study, three sets of experimental runs were performed with the aim of investigating the effects of the main operational parameters. A first experimental screening was performed to determine an appropriate reaction time. The second and third set of experiments corresponded to two rotational central composite designs (RCCD) for optimizing the operational parameters (temperature, catalyst concentration and molar ratio of ethanol to olein), and for investigating the influence of ethanol carried by the resin after its pretreatment. Response surface methodology (RSM) was used to determine an optimal range of operational conditions, guaranteeing conversion higher than 96 % with a catalyst amount corresponding to a range from 10.4% to 11.4% of the oil quantity, a temperature within the range of 55 to 60 °C and a ethanol:oil molar ratio within the range from 3.5:1 to 6.0:1.
Based on the study results, Amberlyst A26 OH resin proved to be viable as a heterogeneous catalyst, allowing high conversion to ethyl esters with the highest amounts of heterogeneous catalyst investigated, temperatures close to the central point and low molar ratios ethanol:oil.