Abstract:

Pulsed electric field ( PEF) was used to enhance the esterification of lactic acid and ethanol,and the influences of electric field strength,temperature and system moisture on the esterification were analyzed. Then,the variation of activation energy during the esterification was explored. The results indicate that ( 1) when the reaction performs with a flowrate of 50 mL /min at 30 ℃,the enhancement by PEF in a certain duration becomes stronger
with the increase in electric field strength; ( 2) by applying 25 kV/cm PEF to the system for 10 h,the production of ethyl lactate is 2. 1 times that of the production without PEF irradiation; ( 3) by applying 20kV/cm PEF for 10h at 25,30 and 35℃,the productions of ethyl lactate are respectively 1. 7,1. 8 and 1. 4 times that of the productions without PEF irradiation; ( 4) PEF treatment is more effective for the system containing water; and ( 5) by applying
20kV/ cm PEF to the esterification system,the activation energy significantly decreases from the original 43. 43kJ /mol to 25. 05 kJ /mol and the stage esterification is a zero-order reaction. The above-mentioned findings indicate that PEF treatment is a promising technique to enhance chemical reaction under non-catalytic condition at room temperature.

Key words: pulsed electric field, lactic acid, ethanol, esterification, ethyl lactate, activation energy