3.4. Activation of catalyst
The results of catalytic activation of water scale-derived catalyst were shown in Fig. 6. The activated catalyst showed excellent catalytic performance, and a biodiesel yield of 91% was achieved with a reaction time of 2 h when the catalyst was activated by 1.5 h,while the biodiesel yield with the nonactivated catalyst was only 50% with the same time. Therefore, it was considered that the biodiesel yield with the nonactivated catalyst was only
50% with the same time. Therefore, it was considered that the pretreatment of methanol could greatly accelerate the catalytic activity of the water scale-derived catalyst [32]. The reason was that a small amount of activated catalyst reacted with methanol and the main component CaO was transformed to Ca(OCH3)2 . Ca(OCH3)2 had a higher basic strength than CaO, which suggest that Ca(OCH3)2 exhibited a higher catalytic activity for the transesteri cation reaction than CaO. Thus the activation of water scale derived catalyst led to the enhancement of its basic strength and a
higher biodiesel yield.