Kinetics of Alkali-Catalyzed Condensation of Impurities in the Cyclohexanone Purification Process

Abstract

In the cyclohexanone purification process, some impurities, such as pentanal, hexanal, and 2-cyclohexen-1-one, must be removed in order to ensure good quality of nylon fibers in the caprolactam polymerization step. To do this, an industrial common practice is to add a homogeneous basic catalyst (such as sodium hydroxide, NaOH) to promote the condensation of these impurities with cyclohexanone because the condensation products are easily separated by distillation. In this study, a kinetic model for the catalytic condensation of each impurity was developed, including variables such as temperature, impurity concentration, and catalyst concentration. In order to fulfill this purpose, runs were carried out in a batch reactor containing 70 g of cyclohexanone and different contents of impurities. NaOH was used as the catalyst (CNaOH values ranging from 2.5 to 30.0 mmol/kg). Runs were carried out by a nonisothermal procedure; the reaction temperature was changed from 298 to 423 K, and several temperature ramps we...