New insights into reaction-diffusion kinetic coupling in the esterification of acetic acid with isopropanol over niobium pentoxide

Abstract

Three reaction-diffusion kinetic models were developed to explain the kinetics and the mass transfer of the esterification of acetic acid with isopropanol, over niobium pentoxide. The kinetic equations were defined by the pseudo-homogeneous, Eley-Rideal and Langmuir-Hinshelwood-Hougen-Watson models. Firstly, the effect of Nb2O5 calcination temperature was evaluated. Later, the effects of reaction temperature, stirring speed and catalyst loading on the reaction conversion were also evaluated. Method of lines was applied to solve the partial differential equations of the models. The kinetic parameters were estimated using a hybrid combination of particle swarm optimization and non-linear least squares algorithm. The performance of the models was evaluated by statistical metrics and Fisher’s test. Reaction tests showed that conversion increased at higher temperature and catalyst loading, however, it remained constant with increasing stirring speed. The conversion increased by around six times when the temperature was raised from 60 to 90 °C. An increase of 7.27% in the conversion was seen when increasing the catalyst loading from 5 to 6 g. Despite the very good models’ prediction, the reaction-diffusion model with LHHW kinetics was the more accurate to predict the heterogeneous esterification of acetic acid with isopropanol over niobium pentoxide according to the statistical analysis.