Unfortunately, non-edible oils such as crude Jatropha oil usually
have high free fatty acid contents (around 15%) that are beyond the
practical limit of a wide range of base catalysts[8e11]. As such, acid
catalysts should be used. Heteropolacids (HPA) can be used in acid
catalyzed transesterification reaction for biodiesel production as it
possesses strong Brönsted acidity and high water tolerance[12].As
they are non-porous materials and soluble in polar media, efforts to
distribute HPA on suitable porous materials to improve the catalytic
activity are deemed worthwhile.
The immiscible nature, coupled with variation in the density of
reactants (alcohol and vegetable oil) in the transesterification
reaction are responsible for poor interaction between them leading
to poor mass transfer. This leads to low reaction rates which in turn,
increases the reaction time to achieve high biodiesel yield [13,14].
For acid catalyzed systems, it is reported that the reaction under
conventional process usually requires high reaction temperature
due to slow reaction rate[15].