Microwave enhancement of pseudo-irreversible esterification of maleic anhydride with 2-ethylhexanol-1

Abstract

Esterification of maleic anhydride and 2-ethylhexanol-1 has been studied with a focus on the development of technology to accelerate industrial processes for plasticizer production. Plasticizers are products similar to the maleate of 2-ethylhexyl prepared by esterification. Esterification is a reversible reaction with yield limited by a dynamic equilibrium between reactants and products. This limitation is eliminated by continuous distillation of the formed water as an azeotrope with xylol. In this case the esterification is called pseudo-irreversible, because the elimination of water shifts the equilibrium to product side. Esterification is a slow reaction even if catalyzed. The strategy adopted to establish possible ways to increase the speed of esterification processes was the determination of complete kinetic equations for esterification under microwave irradiation and with usual heating. Two sets of statistical delineated experiments were performed, one with conventional electric heating and another with microwave heating. From statistical treatment of experimental data resulted six complete kinetics equations that show the possibility of microwaves enhance the non catalyzed esterification to a velocity comparable to the catalyzed reaction with p-toluene sulfonic acid. Also, show a synergic effect of microwaves with p-toluene sulfonic acid which reduces the global order of esterification to near zero order, making it faster than the usual catalytic reactions. © 2005: Microwave Application Group.