Reaction kinetics of the esterification reaction between ethanol and acetic acid catalyzed by Keggin heteropolyacids

Heteropolyacids (HPAs), such as silicotungstic (HSiW), phosphotungstic (HPW), and phosphomolybdic (HPMo) acids, effectively catalyzed the esterification reaction between ethanol and acetic acid. The catalytic activities of HPAs were in an order of HSiW > HPW > HPMo. The conversion of ethanol was more than 85 % when HSiW catalyst was recycled for 10 times with a low mole ratio of HSiW to ethanol of 4.5 × 10−4:1 at 358 K. A second order reversible kinetic model fitted the experimental data well. The forward activation energies were 36.8, 32.6, and 31.6 kJ mol−1 when HSiW, HPW, and HPMo were used as catalysts at 323–358 K.