0.14%, and Fe 0.0049% by weight percentage. Thermal stabilities
of water scale were investigated by TGA in Fig. 1. The result
showed that carbon dioxide was decomposed from the precursor
with a further weight loss of 43% between 600 and 770 C. Above
800 C, the weight loss remained constant. From these results, it
could be indicated that carbonate was completely converted to
metal oxide by calcining at 800 C. Therefore calcination at
800 C or higher temperature was selected.
Catalytic activity for transesteri cation is closely related to the
basic strength [33–35] and basicity of the catalyst, the basic
strength and basicity of various catalysts were depicted in Table 1