-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.

ResumoO presente trabalho buscou avaliar a utilização da argila KSF e resina Amberlyst ® 15 como catalisadores na reação de esterificação dos ácidos graxos livres (AGLs) do óleo da polpa de Macaúba em etanol. Os resultados obtidos mostram que a resina Amberlyst ® 15 é mais eficiente na esterificação dos AGLs quando comparados com a argila KSF. Nas reações utilizando a resina verificou-se que as variáveis temperatura e quantidade de catalisador apresentaram efeito positivo e significativo sobre a conversão da reação e os melhores resultados foram obtidos quando adicionados 20% de catalisador ao meio reacional (em relação à massa de AGLs). O efeito do tempo de reação foi avaliado e na temperatura de 80 ºC, razão molar (AGL:etanol) de 1:4 e 20% de catalisador, conversões > 90 % são reportadas. Palavras-chave: Óleo de macaúba. Catalisadores heterogêneos. Ácidos graxos livres. AbstractThis study aimed to evaluate the utilization of KSF clay and Amberlyst ® 15 resin as catalysts in esterification reaction of free fatty acids (FFAs) from Macauba pulp oil in ethanol. The results obtained showed that the Amberlyst ® 15 is most efficient for esterification of FFAs when compared with KSF clay. In the reactions using resin it was found that the variables temperature and amount of catalyst presented positive significant effect on the conversion reaction, and the best results were obtained when 20% of the catalyst added to the reaction (in relation to FFA mass). The effect of reaction time was evaluated and at temperature of 80 °C, molar ratio (FFA: ethanol) of 1:4 and 20% catalyst, conversions > 90% are reported.

In this study, the production of fatty acid ethyl esters (FAEE) from macauba pulp oil and pressurized ethanol was investigated. The experiments were conducted without the addition of catalyst, at 20 MPa, to determine the effect of temperature (200 to 300 °C) and the oil to ethanol mass ratio (1:1 and 1:2) on the FAEE content and different residence times (10 to 45 min). The effect of the addition of n-hexane to the oil (20 wt%) as a co-solvent was also evaluated. The use of high temperatures (275 and 300 °C) resulted in high FAEE content (∼90%). Increasing the amount of ethanol in the reaction medium contributed to the formation of esters only at operating temperatures of 200 to 250 °C. It was also observed that with the addition of co-solvent (in the oil) it was possible to obtain high amounts of FAEE in a shorter reaction time. In addition, a low content of unreacted compounds (∼8.0%) and the conversion of ∼90 and 99% of the free fatty acids and triglycerides were observed, respectively.