The undesirable by-product
namely dialkyl ethers are also formed due to etherification
reactions under harsh reaction conditions [28]. These stringent
conditions are not favorable from economic and industrial point
of view. Besides these catalysts, only few studies have been
reported for esterification of palmitic acid on SZr solid acid catalyst [27,29]; however higher acid to methanol ratio (1:40) and
catalyst amount (15 wt%) are reported to obtain 89–97% conversion of palmitic acid at 60–95 C temperature. SZr incorporated
in SBA-15 has also been reported to exhibit 89% conversion at
68 C with a higher acid to methanol ratio of 1:80 [29]