Esterification of propionic acid under microwave irradiation over an ion-exchange resin

Esterification of propionic acid with ethyl alcohol over an ion-exchange resin catalyst was studied under microwave dielectric heating. Experiments were carried out in a single-mode microwave loop reactor, equipped with a heating band as well to directly compare the efficiency of the conventional convective/conductive heating and microwave dielectric heating. Series of kinetic experiments were carried out with both conventional and dielectric heating at the reaction temperature of 105 °C and total pressure of 7 bar. Different initial molar ratios of propionic acid-to-ethanol (from 1:2 to 2:1) were investigated. Initial molar ratios of acid-to-alcohol significantly affected the final yield of the desired product ethyl ester of propionic acid, ethyl propionate. The highest product yield was observed with equimolar initial ratio, compared to 1:2 and 2:1 initial molar ratios of acid-to-alcohol. However, the kinetics and equilibrium of this reaction were unaffected by the method of heating (microwave or conventional).