Enzymatic conversion of corn oil into biodiesel in a batch supercritical carbon dioxide reactor and kinetic modeling

Synthesis of fatty acid methyl esters (FAME) as biodiesel from corn oil was studied in a batch supercritical carbon dioxide (SC-CO2) bioreactor using immobilized lipase (Novozym 435) as catalyst. Effects of reaction conditions on the contents of FAME, monoacylglycerols (MAG), diacylglycerols (DAG), and triacyglycerols (TAG) were investigated at various enzyme loads (5–15%), temperatures (40–60 °C), substrate mole ratios (corn oil:methanol; 1:3–1:9), pressures (10–30 MPa), and times (1–8 h). The highest FAME content (81.3%) was obtained at 15% enzyme load, 60 °C, 1:6 substrate mole ratio, and 10 MPa in 4 h. A reaction kinetic model was used to describe the system, and the activation energy of the system was calculated as 72.9 kJ/mol. Elimination of the use of organic solvents, chemical catalysts and wastewater as well as reasonably high yields make the enzymatic synthesis of biodiesel in SC-CO2 a promising green alternative to conventional biodiesel process.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Corn oil was successfully converted to fatty acid methyl esters in a batch SC-CO2 bioreactor. ► Expanded reaction medium under moderate pressure resulted in high yields due to improved mass transfer. ► Reactions in batch SC-CO2 bioreactors are inhibited at lower levels of excess alcohol compared to continuous ones. ► Biodiesel conversion in SC-CO2 media is a green technology which eliminate the use of organic solvents, chemical catalysts, and wastewater.