New insights in biodiesel production using supercritical 1-propanol

• New insights in biodiesel production using supercritical 1-propanol.
• Biodiesel yield as high as 93.8 wt% was achieved at 350 °C after 30 min.
• The developed kinetic model expressed the experimental data well.
• 1-Propanol has low reactivity compared to methanol and ethanol.

In this study, for the first time, continuous biodiesel production and the related reaction kinetics in supercritical 1-propanol (SCP) were investigated. This study aims to investigate the reaction characteristics of biodiesel production using SCP and to elucidate the kinetics. The experimental conditions were as follows: temperature, 270–400 °C; residence time, 5–30 min; a fixed pressure of 20 MPa; and an oil-to-1-propanol molar ratio of 1:40. A model of the detailed reaction kinetics for biodiesel production in SCP was developed, and the biodiesel yields obtained in this study were compared with those in supercritical methanol and ethanol (SCM and SCE). The result showed that the biodiesel yield in SCP increased with temperature and time. The detailed kinetic model was found to agree well with the experimental data. The reactivity of SCP was lower than that of SCM and SCE. The activation energies for the conversion of triglyceride to diglyceride, diglyceride to monoglyceride, and monoglyceride to glycerol were about 111.39, 78.99, 60.96 kJ mol−1, respectively.