Zeolite BEA catalysed esterification of hexanoic acid with 1-octanol: Kinetics, side reactions and the role of water

In recent years, solid acid catalysts such as zeolite BEA are increasingly applied in esterification and etherification reactions, especially in reactive distillation and reactive stripping. In this study, the kinetics of the zeolite BEA catalysed esterification of 1-octanol with hexanoic acid and its side reaction, the etherification of 1-octanol, has been determined. Both reactions can be described using a Langmuir-Hinshelwood type approach accounting for the reversibility of the esterification reaction, limiting the conversion level. The influence of the water concentration on the esterification kinetics was investigated using a closed reactor system. The adsorption of water is 38 times stronger than that of 1-octanol while the adsorption of hexanoic acid, ester and ether are negligible. The formation of octene is not considered in the kinetic model as it was found that octene is formed by ether splitting when mass transfer limitations play a role. Therefore its formation is negligible in kinetic experiments using a powder catalyst. The kinetic parameters determined in this study allowed direct prediction of the instantaneous selectivity as a function of the reaction coordinate of the esterification and of the fraction of water removed. These predictions were validated by data from pilot scale reactive stripping experiments. (C) 2009 Elsevier B.V. All rights reserved.