| Summary: | Due to the growing interest in the production of flavor esters with a variety of applications in global markets, this work proposed an efficient and practical catalyst solvent-free microwave-aided esterification (MAE) method to produce ethyl lactate. To this end, MAE via different catalysts including Amberlyst 15 Dry, Amberlyst 36 Dry, Amberlyst 16 Wet, and Amberlite IR-120 was investigated and then the effect of esterification conditions on production yield was studied. Among catalysts, the highest ethyl lactate yield (56.57 %) was achieved after 120 min of microwave radiation in the presence of 4 % (w/v) Amberlyst 15 Dry and 1:4 mole ratio of lactic acid:ethanol. It was due to its higher average pore size, surface area, and total exchange capacity than Amberlyst 36 Dry, Amberlyst 16 Wet, and Amberlite IR-120. Increasing the lactic acid:ethanol mole ratio to 1:6 and Amberlyst 15 Dry concentration up to 6 % decreased ethyl lactate yield at the end of esterification time to 39.54 % and 40.56 %, respectively. As compared to ultrasonic bath-aided esterification (UBAM) and magnetic stirrer-aided esterification (MSAE), the lowest structural damage to the catalyst as well as the lowest specific energy consumption (0.045 kWh/g ethyl lactate) and specific CO2 emission (36 g/g ethyl lactate) was achieved under MAE. Therefore, MAE as a more energy-efficient and environmentally friendly method can provide the opportunity for the commercial production of flavor esters with relatively high yields.
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