2.4. Catalytic activation
The catalytic activation of water scale-derived catalysts was as
follows. A certain proportion of methanol and catalyst were added
in the ask equipped with a re ux condenser and stirred for 1.5 h
at 25 C for activation. Then, a proportional amount of soybean oil
was added to the mixture and stirred [32]. The transesteri cation
reaction conditions and post treatment were as the above reaction
procedure.