Production of palm-based glycol ester over solid acid catalysed esterification of lauric acid via microwave heating

This study involved in maximizing the conversion of lauric acid to glycol ester via esterification with diethylene glycol, aided by calcined Zn-Mg-Al catalyst in a 250-ml reactor using microwave heating. Preliminary catalytic screening involving three types of catalysts (tin (II) oxalate, Amberlyst-15 and calcined Zn-Mg-Al), resulted in the conversion of lauric acid obtained were 65.4%, 31.6% and 95.4% using tin (II) oxalate, Amberlyst-15 and calcined Zn-Mg-Al, respectively. In addition, conversions obtained from the solid acid catalysts appeared to be higher than autocatalytic esterification of only 15.8%. The optimum operating condition for esterification via microwave heating was established at 190 °C, 2:1.3 mol ratio of lauric acid to diethylene glycol with 5% of catalyst dosage at 90 min. Calcined Zn-Mg-Al catalyst under optimised condition gives 98.2% of lauric acid conversion. The recyclability of the catalysts in the esterification of lauric acid with diethylene glycol were also carried out. It shows that calcined Zn-Mg-Al and tin (II) oxalate both can be used for six cycles as compared to Amberlyst-15 catalyst that has lost part of its activity after the third cycle. The microwave heating remains attractive for heating catalytic esterification as it accelerates the reaction speed at shorten period of time from 8 h to 1.5 h as compared to conventional heating.