Additionally, the acidic character of the alcohols used decreases
as the chain increases, so the methanol is the alcohol more acidic,
because a larger chain stabilises the OH group; the 3-methyl-1-
butanol is the less acidic, it is clear that this is directly associated
with the biodiesel production; this research shows that the acidity
or basicity of the alcohol used directly influences the production
of biodiesel. The degree of deactivation was found to be
inversely proportional to the number of carbon atoms in the linear
lower alcohols. Fig. 6 shows the stabilising effect of the branched
chain alcohols and linear alcohols used on the immobilised lipase.
The degree of stability brought out by the branched alcohols
was demonstrated to be greater than that by the linear alcohols.
The curves for 3-methyl-1-butanol, 2-methyl-1-butanol and 2,2-
dimethyl-1-propanol in Fig. 6 are less pronounced than in the case
of linear chain alcohols. It was also observed that when the immobilised
lipase was decreasing its stability by methanol or ethanol,
the immobilised lipase particles underwent a conspicuous change
in appearance, accompanied by swelling and caking. This work
has shown that alcohols with more than three carbon atoms were
completely miscible with palm oil at the molar ratio researched.
The experimental results indicated that one of the main causes of
the decrease of the lipase was due to the immiscibility between
triglycerides and short chain alcohols (i.e. methanol or ethanol). It
is possible that the short linear alcohols employed formed small droplets which attached to the resin particles. As the alcohol was
adsorbed to the immobilised enzyme, the entry of triglycerides was
blocked, causing the reaction to stop. Table 2 shows the behaviours
of the biodiesel yield as a function of time in the different alcohols.
Candida antarctica B lipase was immobilised on FC-6 and FC-4 and
used as a catalyst (biocatalyst) that present a highest yield with
FC-6.