To produce
biodiesel from high
free fatty acid (FFA)
oils, the
esterification characteristics of two kinds of
heterogeneous acid catalysts,
Amberlyst 15 and
Amberlyst BD20, were compared. When the FFA contents of
oils were 50.0 and 99.8 wt%, the activity of
Amberlyst 15 gradually decreased with recycling, whereas the activity of
Amberlyst BD20 was maintained during recycling. The activity of
Amberlyst 15 was inhibited by the
water produced during the
esterification process, but the activity of
Amberlyst BD20 was not similarly affected by
water. In images obtained with a
scanning electron microscope (SEM), many pores were seen within the
Amberlyst 15
catalyst, whereas
Amberlyst BD20 showed few pores. Despite the fact that the pores of the
catalyst play a role in increasing the number of
active sites,
Amberlyst BD20, which had fewer pores, was deemed to have more desirable performance in reducing the inhibition by
water of the
esterification of high FFA
oils.
