Investigations were conducted on a series of calcium and
lanthanum oxides catalyst for biodiesel production. The optimum
transesterification condition was selected based on Response Surface
Methodology (RSM) optimization tool that similar to our
previous study [30]: 160 C, methanol/oil molar ratio of 25, catalyst
loading of 3 wt.% in 3 h of reaction time. For CaOeLa2O3 catalyzed
transesterification, higher reaction temperature are needed to give
a satisfactory conversion as compared to that of several previous
mixed metal oxides studies (CaOeMgO and MgOeZnO) [16,31]. The
transesterification temperature (160 C) at moderate pressure able
to enhance oilemethanol miscibility (by reduce heterogeneous
phase separation) and increase rate of reaction, leading to a shorter
reaction time. Moreover, higher temperature minimizes the initial
mass transfer limitation in transesterification system. When the
reaction temperature reached 160 C, the vapor pressure of methanol is ~2.0 MPa, which will favor transesterification reaction
under this high pressure and temperature