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

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 200 bar at 70 degrees C. Reaction conversions as high as 90% were obtained at 200 bar, 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 largescale 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. (C) 2014 Elsevier B.V. All rights reserved.