.The transesterification reactions were carried out in a 250 ml
3-necked round bottomed flask. The middle neck was used
to insert a mechanical stirrer (BioLab BL 232 D), one of the
side necks was fitted with a water-cooled condenser, and the
other neck was fitted with a temperature indicator. The speed
of the mechanical stirrer was monitored by using an analog
tachometer (Fuji Kogyo Co. Ltd., Kyoto). The desired amount
of catalysts, methanol and waste frying oil was introduced into
the round bottomed flask and the reactions were carried out at
65 C for 1 h. After the reaction is completed, the catalyst was
separated by filtration and the transesterification products
were allowed to settle overnight for the clear separation of biodiesel
and glycerol. The conversion of oil to fatty acid methyl
esters was analyzed by 1
H Nuclear Magnetic Resonance Spectroscopy
(1
H NMR) using a Bruker Avance III 500 MHz (AV