2.2. Catalyst preparation
Highly active CaO catalyst was prepared by the calcination–
hydration–dehydration treatment of egg shells.
Egg shells were washed thoroughly in tap water to remove any unwanted material adhered on its surface, and rinsed twice with distilled
water.
The washed egg shells were then dried in hot air oven at
105 _C for 24 h.
The dried egg shells were reduced to small
pieces and calcined in a muffle furnace under static air conditions
at 900 _C for 2.5 h to transform the calcium species in the
shell into CaO particle (denoted as Egg shell-CaO-900).
Then the CaO derived from the egg shell was refluxed in water at
60 _C for 6 h and the solid particle was filtered and dried in
hot air oven at 120 _C overnight [27].
The solid product was dehydrated by performing calcination at 600 _C for 3 h to change the hydroxide form to oxide form. Thus the egg shells
subjected to the calcination–hydration–dehydration treatment
generate a highly active CaO (denoted as Egg shell-CaO-
900-600).
Anhydrous methanol of analytical grade and commercial CaO purchased from Merck Limited, Mumbai, India were used in the transesterification
reaction.
Commercial CaO was treated in the muffle furnace
at 600 _C for 3 h before use.