Kinetic modelling of the esterification of rosin and glycerol: Application to industrial operation

The esterification of glycerol and rosin is a reaction of importance in the coating and adhesive industries, main consumers of the triglyceride of rosin acids. While this chemical transformation has led to some of the most useful products of rosin, kinetics of the reactions involved have not been studied in depth. In this study, a new analytical method based on gel permeation chromatography (GPC) is applied and compared to classical acid titration, the industrial standard. Experimental data on rosin esterification with glycerol were obtained at laboratory scale, covering a wide range of operational conditions, changing rosin to glycerol molar ratio (between 2 and 4) and temperature (between 240 and 280 °C). Afterwards, different kinetic models were fitted to experimental data to select between first- and second-order potential and hyperbolic kinetic models. Linear and non-linear regression techniques with numerical integration of the differential equations were used to fit the proposed kinetic models. A hyperbolic model coupled with glycerol mass balance that considered stripping of this polyalcohol proportional to the global reaction rate and to glycerol concentration proved to be the most adequate both at a given temperature and in all the temperature intervals studied. On the other hand, samples were analysed by H NMR and ionic chromatography to determine the glycerol amount in the reaction medium and in the distillate, respectively, observing the stripping of the polyalcohol. Finally, the selected model was used to simulate and fit runs executed at the usual industrial mode, a transient temperature operation followed by an isothermal operation with gradual addition of glycerol (fed-batch operation). These runs were performed at lab and at industrial scale, and the selected kinetic model and glycerol mass balance were adequate to simulate rosin conversion.