ABSTRACT This study evaluated the potential of macauba pulp oil (MPO) as a feedstock for continuous ester production using ethanol under pressurized conditions. Experiments were performed in order to obtain data for the effect of process variables on ethyl ester (FAEE) and free fatty acid (FFA) conversion in a catalyst-free process. From the results, it appears that the MPO to ethanol mass ratio and the pressure were the variables with more favorable effect on the evaluated response variables. The addition of n-hexane caused an increase in the production of esters; however, this had a negative effect on FFA conversion. The addition of water was unfavorable for oil processing with high acidity. In this process, esterification and transesterification occur simultaneously, and the high FFA content in MPO provides high yields (85 wt% of esters; 93% FFA conversion) at low temperature, since the esterification reaction rate is higher than the transesterification. The decomposition of fatty acids was evaluated and levels <5% were observed under the evaluated experimental conditions.

In the present study, the transesterification of Jatropha oil in a continuous catalyst-free process using supercritical ethanol was investigated. Experiments were performed in a packed-bed tubular reactor by studying the effect on the reaction of temperature, pressure, water and cosolvent (n-hexane) concentrations, keeping the oil:ethanol mass ratio fixed at 1:1 for different residence times. The results demonstrated that temperature and pressure had a positive effect on fatty acid ethyl ester (FAEE) production and it was observed that the free fatty acids present in vegetable oil promote faster reaction kinetics due to simultaneous esterification and transesterification reactions. The addition of water and a cosolvent increased the FAEE yields at 573 K and 20 MPa. Within the experimental ranges investigated, water and the cosolvent decreased the decomposition of fatty acids. Appreciable reaction yields (~90 wt%) were achieved at 573 K, 20 MPa, with an oil:ethanol mass ratio of 1:1 and 10 wt% water.