PROCESS INTENSIFICATION IN THE ESTERIFICATION OF ROSIN WITH GLYCEROL
Special Symposium - EPIC-1: European Process Intensification Conference - 1
EPIC-1: Poster Session (EPIC - Poster) - P2
Keywords: Rosin, glycerol, esterification, solubility, intensification
PROCESS INTENSIFICATION IN THE ESTERIFICATION OF ROSIN WITH GLYCEROL
Ladero; M. 1; de Gracia, M. 1; Trujillo, F.2; Garcia-Ochoa, F. 1
1 Dpto. Ingenieria Quimica. Fac. CC. Quimicas. Universidad Complutense. 28040- Madrid. Spain.
2 La Union Resinera Española, S.A., Madrid, Spain.
e-mail: mladero@quim.ucm.es
Rosin is the non-volatile fraction obtained in the distillation of pitch. The esterification of rosin with polyhydric alcohols produces a series of several esters of importance in the sizing of paper, in adhesives, in the formulation of several polymers for their use in coatings and devices for the controlled release of fertilizers and drugs, and more. One of the most commonly used esters is the rosin-glycerol tri-ester. This product is obtained traditionally by a thermal activation of the acid, rosin, at high temperatures (260 ºC or higher) [1].
The aim of this work is to study the relationship between the physical distribution of phases in the reaction media and the kinetics of the thermal esterification. Moreover, the effect of both a catalyst and a related surfactant on the chemical and physical enhancement of the reaction rate will be considered in the present work.
In a previous study, the statistical and physical selection among several kinetic models for the esterification between glycerol and rosin has been performed [2]. A hyperbolic kinetic model was selected as the best one to fit data at several temperatures and initial concentrations of glycerol. Esterification reaction rates are usually well described by first- or second-order kinetic models [3]; the need of the hyperbolic model was supposed to be due to the presence of two phases at the beginning of the reaction, one of them of pure glycerol. The use of SEM and optical microscopy confirmed this fact. A thorough study of the solubility of glycerol in rosin showed that the phase distribution depends much on the temperature and the quantity of glycerol, and a solubility curve with temperature was obtained. It was observed by SEM that the reaction medium proceeds from an initial two-phase medium to a one-phase one when theoretical glycerol concentration was under its solubility at the reaction temperature.
With the previous observations, it was hypothesized that the reduction of the drop size in the two-phase system or the existence of a one-phase one could enhance the reaction rate. P-toluensulfonic acid (PTSA) and its chloride (PTSC) were added at several concentrations (from 0.01 % to 0.1 % in weight with respect to rosin). The acid is a known esterification catalyst, while the chloride, in a low water liquid, could behave as a surfactant. With both compounds, an enhancement of the initial reaction rate was observed: more than four times with 0.06 % PTSA and more than twice with the same amount of PTSC. The observation of the samples by SEM renders the same result in both cases: the initial two-phase system evolved from one containing great drops of glycerol to others with smaller drops, and the evolution to the one-phase system was faster with both compounds. The solubility enhancement is evident and its correlation to the enhancement of the reaction rate is well established, as well, as the reaction rate is proportional to real glycerol concentration (as is usual with other well solved alcohols).
References:
[1] Smith, T. L. and Elliot, J. H. J. Am. Oil Chem. Soc. 35, 692-699 (1958).
[2] Calzada, J.; Bonilla, G.; Ladero, M.; Fernandez, V.; Trujillo and F.; Garcia-Ochoa, F. 10th Mediterranean Congress on Chemical Engineering. Barcelona (2005).
[3] Salmi, T.; Paatero, E. and Nyholma, P. Chem. Eng. Process. 43, 1487-1493 (2004).
See the full pdf manuscript of the abstract.
Presented Thursday 20, 13:30 to 14:40, in session EPIC-1: Poster Session (EPIC - Poster) - P2.
