In order to clarify the contribution of leached Ca2þ to the overall
biodiesel yield, following investigation test on CL8.0 catalyst was
performed. The fresh CL8.0 catalyst was first stirred with certain
amount of methanol (25:1 methanol to oil ratio) at usual transesterification
condition (160 C and 3 h). Subsequently, the stirred
catalyst was then filtered out and the methanol filtrate was reacted
with fresh jatropha oil under the same reaction condition. It was
observed that 8% of FAME yield was obtained from the first run
(Table 6), which means that 8% from total of 98.76% of the FAME
yield was contributed by the presence of leached Ca2þ homogeneous
catalyzed reaction. The second and third leaching experiment
showed the decreased of FAME yield at 5 and 4%, respectively,
while the control experiment (without catalyst) renders 3% of
FAME yield. This give a clear indication that low content of soluble
Ca2þ species from CL8 binary system which only make a minor
contribution of homogeneous-type transesterification. This leaching
test is in agreement with the reusability study where the overall
FAME yield was decreased sharply for 1st cycle while maintain at
>80% for next continuous cycles. The results for reusability and
leaching test were well correlated with the testing of Ca content in
biodiesel product by using AAS analysis. The concentration of
leached Ca2þ was found in high concentration (26 ppm) for firstrun
biodiesel, while the second and third-run products rendered
lower Ca content in 12 and 12 ppm, respectively.