The effect of methanol/oil molar ratios on FAME yield over
meretrix venus shell-derived catalyst (calcined for 4 h) was investigated.
The FAME content increased significantly by increasing the
methanol/oil ratio from 9 to 12. This higher amount of methanol
would promote the formation of methoxy species on CaO surface,
and should also shift the reaction equilibrium to the forward direction.
However, further increase in methanol/oil ratio up to 18 did
not promote the reaction. It was considered that the glycerol
would largely dissolve in excessive methanol and subsequently
inhibited the reaction of methanol to the reactants and catalyst.
The optimum MeOH:oil ratio was 12:1 over the catalyst in the
present study, which was double the practical MeOH:oil ratio for
homogeneous transesterification of 6:1.