Apart from the advantages like rate enhancement, increased
yield, and improved purity from the supercritical process it has
some drawbacks like high equipment cost and high energy consumption
due to high temperature and pressure conditions. This
limits the supercritical transesterification process to be viable for
large scale industrial applications [29]. However, the introduction
of co-solvents like hexane, carbon dioxide, and calcium oxide into
the reaction mixture decreases the severity of the reaction parameters
and can make this process practical. The addition of cosolvents
can decrease the critical point of alcohol and allow the
supercritical reactions to be carried out at milder temperatures
[30–33]. Our previous studies have shown increased yield when
hexane was added as co-solvent in the transesterification of camelina
sativa oil under supercritical ethanol conditions [3]. The cosolvent
in the reaction mixture can increase the mutual solubility
of the oil and alcohol at lower reaction temperatures and accelerates
the reaction rate at supercritical conditions [22].