Fast and energy efficient glycerol esterification with lauric acid by near and far-infrared irradiation: Taguchi optimization and kinetics evaluation

Abstract

This article explores efficacy of infrared irradiation for intensification of glycerol esterification with lauric acid. Effects of in-situ water removal employing molecular sieve or silica gel desiccants on lauric acid conversion have also been assessed. Glycerol esterification with lauric acid was optimized through Taguchi orthogonal approach employing an infrared irradiated reactor operated in far-infrared region (2700–30,000 nm). At optimal conditions (80 °C temperature, 6.2 glycerol to lauric acid molar ratio, 900 rpm stirrer speed and 5 wt.% catalyst concentration), infrared irradiated reactor rendered 99.0% lauric acid conversion and a tungsten halogen irradiated reactor operated in near-infrared region (360–2000 nm) resulted 97.6% conversion; while a reactor employing conventional conductive heating protocol resulted relatively lower 95.2% lauric acid conversion. Notably, infrared irradiated and tungsten halogen irradiated reactors consumed only one-third and half of the energy required for conventional conductive reactor, owing to appreciably lower reaction activation energy. Reaction rate constants were considerably higher for infrared irradiated and tungsten halogen irradiated reactors compared to that of conventional conductive reactor. GC–MS study of energy-efficient infrared irradiated reactor product demonstrated appreciable selectivity (80.2%) to glyceryl monolaurate. It is expected that the application of infrared irradiated reactor will facilitate energy-efficient and fast conversion of other fatty acids into corresponding glyceryl esters.