Abstract
The “macaúba” (Acrocomia aculeata) is a Brazilian palm tree that represents a promising alternative for the production of biodiesel. The kernel and the almond of the fruits are rich in oil. Its oil has interesting physicochemical characteristics for the production of biodiesel. It consists mainly of triacylglycerols and small amounts of mono and diacylglycerols, and it has a high content of unsaturated fatty acids, mainly oleic acid. However, it has a high content of free fatty acids which prevents reactions with basic catalysis for biodiesel production. The use of solid catalysts to improve the biodiesel production processes is considered as a promising alternative in this case. In addition, the solid catalysts have the highest reaction rate when compared to acid catalysts. The aim of this study was to obtain ethyl esters of crude oil from A. aculeate withhigh acid value (45.3 mg KOH g-1), using heterogeneous catalyst, with low reaction temperature. Thereactions were done in an under-pressurized Parr 4843 reactor. For the reaction, the factorial design is 2 elevated to 2 and response surface methodology was used. The variables studied were: temperature (T), molar ratio (MR) (ethanol:oil) and catalyst Amberlyst 15 (C, wt%). The response was obtained into yield (%) of ethyl esters and conversion (%) of free fatty acid, which were quantified by gas chromatography (GC). The response surface indicated the reaction at temperature 80-100 °C, molar ratio ethanol:oil 9.0:1 and catalyst 9- 11 wt% presented an yield in 32.8% of fatty acid ethyl esters (FAEE) and 72.0% of conversion, with 48.8 of selectivity index. The Amberlyst 15 catalyst showed little selectivity for yield in terms of FAEE, but a greater conversion of free fatty acids (FFAs) to the respective ethyl esters occurred. The surface response graph indicated that the reaction medium at temperature 60-70 °C, ethanol:oil 8.0:1-9.0:1 and catalyst 2-4% wt provided 83.8% of FFA conversion. This result is expected for oils with high FFA content, since conversion occurs at lower temperatures, while good yields occur at elevated temperatures.
