These results
indicate that the solid base catalyst, Sr2SiO4, seems to be less effective,
when compared with NaOH, and unsuitable for use to catalyze
the transesterification of the extracted microalgae oil under the
current conditions.
There are two possible reasons that may cause the decrease in
chlorophyll content during the transesterification with an increase
in the dose of base catalysts that were mixed with methanol at a
fixed catalyst to methanol ratio. First, chlorophyll may dissolved
in methanol and then moved to the methanol (polar) phase. This
will cause a decrease in the chlorophyll content in the biodiesel
produced (mainly located in the hexane phase). Second, the base
catalyst may easily react with chlorophyll causing its decomposition
as mentioned in the literature (Han et al., 2013).