Successful alkali base catalyzed transesterification process requires lower FFA content in CJCO, which is less
than 2%. However, Table 2 indicates higher FFA content
in CJCO sample, which is about 15%. Although Fig. 2
shows the result of direct transesterification of CJCO using
basic catalyst, by direct transesterification, methyl ester
yield of CJCO was only 55%, which was very low yield
comparing to methyl ester yield of CPO and NCO. Thus,
it is clear that high FFA content in the oil affected the
methyl ester yield.
The two-stage transesterification process of CJCO
showed higher methyl ester yield than single stage or direct
transesterification process. After acid pretreatment/acid
catalyst esterification, FFA in the oil moved into methanol
phase. The cleaned oil was brought to the second stage,
base catalyzed transesterification with only NaOH to oil
ratio at 1% w/w. In the second stage, the low level of
remained FFA from the first stage clearly affected the
transesterification process. Therefore, investigation of optimum catalyst to oil ratio and optimum methanol to oil
ratio was required. Fig. 4 shows that the optimum catalyst
to oil ratio was 1.4% w/w and optimum methanol to oil
ratio was 24% w/w. At this optimum condition, the methyl
ester yield was 90%, which was higher than the methyl ester
yield of direct transesterification.