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

•Soybean biodiesel production using SC-CO2 was investigated in a continuous expanded-bed reactor.•Reaction of 90% was obtained at 200 bar, oil to ethanol molar ratio of 1:9, and substrate to solvent mass ratio of 1:3.•Continuous enzymatic process of biodiesel using SC-CO2 showed to be a promising technology for large-scale purposes.

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 (10–70 g), 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 °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 40 g 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.

Graphical abstractInfluence of pressure on biodiesel conversion in the continuous expanded-bed reactor using SC-CO2 as co-solvent. Substrate to solvent mass ratio and soybean oil to ethanol molar ratio were kept at 1:3 and 1:9, respectively, using 30 g of enzyme and 70 °C. Legend: ●100 bar and substrate to solvent ratio of 1:3, ■ 148 bar and substrate to solvent ratio of 1:2, ♦ 200 bar and substrate to solvent ratio of 1:3.Figure optionsDownload full-size imageDownload as PowerPoint slide