CaO/NaA combined with enzymatic catalyst for biodiesel transesterification

We combined CaO/NaA with enzymatic catalyst to produce biodiesel at moderate temperature and studied the Arrhenius model of the combined reaction. This transesterification reaction with molar ratio of methanol to olive oil 3:1, was speculated to be the fourth order reaction by formula calculation. The Ea of the first stage catalyzed by CaO/NaA was 37.92 kJ/mol, and that of the second stage catalyzed by lipase was 73.98 kJ/mol. The lipase activity was repressed in the second stage. The combined transesterification reaction did not completely inactivate the enzymatic catalyst, which was still active in the second stage of reaction and further improved the conversion efficiency. The maximum FAME product conversion yield was optimal 94.5% after reaction catalyzed by CaO/NaA at 40 °C for the first 3 h and catalyzed by lipase for the next 3 h.

► We combined the basic and enzymatic catalyst to produce biodiesel.
► The reaction without excess methanol was speculated to be the fourth order model.
► The combination reaction did not inactivate the enzymatic catalyst.
► The lipase was still active and further improved the yield to optimal 94.5% at 35 °C.