Estudo da catálise enzimática para produção de biodiesel a partir de óleo residual de andiroba (carapa guianensis aubl.)

Abstract

Andiroba (Carapa guienensis Aubl.) is considered the most explored oilseed plant species in the Brazilian Amazon and a large amount of residues are generated due to its exploitation. In this work, we evaluated modern concepts adopted by biorefineries, in order to better use the raw materials and the residues of andiroba. The marc produced during the extraction of seeds of andiroba by mechanical pressing was chemically extracted by maceration with hexanes. We obtained 10% of andiroba residual oil that contained 2% of limonoids. These compounds have commercial value because of their biological properties. We were able to separate these compounds from the oil by open column chromatography over silica gel and DIAION HP-20. Two fractions were obtained, one containing the limonoids along with free fatty acids and a second mostly containing triacylglycerides. Then the andiroba residual oil (free of limonoids) was evaluated to produce biodiesel by a two-step process involving enzymatic hydrolysis with lipase and esterification by heterogeneous catalysis, with methanol and ethanol. First the hydrolytic activity of different commercial available lipases was assayed with andiroba residual oil as substrate. The lipase from Candida rugosa showed the best results. The best enzymatic conditions were determined by central composite and response surface design. The optimal conditions, considering a 94% rate conversion were determined at 50°C, pH=7,0 and 10% of substrate. These conditions were experimentally confirmed at larger scale in a glass-reactor. We have also evaluated the reuse of the enzymatic fraction in different reaction cycles and were able to reuse it twice with steady yield of 92%. The time-course and yield of all enzymatic reactions were determined by TLC-videoscan technique to ensure the reliability of results. The esterification step was achieved with 2% of Fe2(SO4)3, a molar ratio of oil and alcohol of 1:6, at 70°C (ethanol) and 60°C (methanol). The yield obtained for biodiesel was 86% and 91% for ethanol and methanol, respectively. The obtained results for this two-step process (enzymatic hydrolysis followed by esterification by heterogeneous catalysis) with andiroba residual oil were very promising, especially to ethyl biodiesel production.