Sequential process for obtaining methyl esters and triacetin from crambe oil using pressurized methyl acetate

Abstract

The aim of this study was to investigate the application of a sequential process for the production of fatty acid methyl esters (FAME) and triacetin (TA) from crambe seeds using methyl acetate (MA) under pressurized conditions. In this process, methyl acetate acts as an extraction solvent and an acyl acceptor for the conversion of the oil to the products of interest. The initial step was pressurized liquid extraction (PLE) performed in a semi-continuous experiment (140 °C and 10 MPa) and material resulting from this step (oil+MA) was directed to a continuous reaction unit. The tests were performed with different pressures, temperatures and residence times. Reactions with commercial oil (CO) were evaluated for comparison. According to the data obtained, increasing the pressure to 20 MPa resulted in higher FAME yields (YFAME) and TA contents for both oils tested. In the reaction with the PLE mixture an increase in temperature favored the formation of FAME and a yield of 66.49 % was achieved at 375 °C after 15 min. The TA content was highest at 325 °C and 5.01 wt% of this coproduct was obtained after 35 min. At the other temperatures, an increase in the TA content was not observed after 15 min. The results obtained in the reactions with CO demonstrated lower than those for the oil obtained by PLE and the reduction of polyunsaturated esters was more evident in the reaction products of this oil. At 375 °C, the increase in residence time provided higher conversion of triglycerides and free fatty acids, as well as higher consumption of intermediate reaction compounds, and enhanced levels of thermal degradation. Thus, the results point to the benefits of using the sequential process to obtain FAME and TA in terms of yield and reduction of the decomposed fraction.