Enzymatic synthesis of soybean biodiesel using supercritical carbon dioxide as solvent in a continuous expanded-bed reactor

Abstract

The enzymatic synthesis of soybean biodiesel using supercritical carbon dioxide (SC-CO2) as solvent in a continuous expanded-bed reactor was investigated. For this purpose, the commercial immobilized lipase Novozym 435 was used as catalyst and the variables investigated were the amount of enzyme (10–70g), oil to ethanol molar ratio (1:9–1:21) and substrate to solvent mass ratio (1:1–1:3), pressure ranging from 100 to 200bar at 70°C. Reaction conversions as high as 90% were obtained at 200bar, oil to ethanol molar ratio of 1:9, substrate to solvent mass ratio of 1:3 using 40g of enzyme. The continuous process for enzymatic synthesis of biodiesel using SC-CO2 showed to be a promising technology for large-scale purposes. The proposed system demonstrated to be possible to obtain high conversion using lesser enzyme than in a packed-bed reactor, which might be an important advantage, due to the exhibited enzyme high-costs.