Page 129 - Refining Biomass Residues for Sustainable Energy and Bioproducts

100 Refining Biomass Residues for Sustainable Energy and Bioproducts

compound, respectively. The results are directly obtained in a very short span of
time after analysis without any complex pretreatment, but it should be done with
precision sampling because even moisture and carbon dioxide can mask and inter-
fere with the results. And also, traces of chemical compounds are underestimated or
erased due to the high intensity of certain other infrared bands (Horgnies et al.,
2013). Apart from these standard methods discussed above, other techniques such
as C 13 NMR, Raman spectroscopy, CHNS (O) analysis, and NH 3 -TPD are also used
occasionally.

4.6 Parameters affecting the reactions

The molar ratio of methanol to oil is a noteworthy factor that affects catalytic per-
formance. The methanol quantity needs to be high to force the reaction toward bio-
diesel formation (Kouzu et al., 2009). In general, an increase in this ratio helps to
improve triglyceride conversion to a larger extent.
Le Chatelier’s principle says that the usage of lesser amount of methanol during
biodiesel production decreases its yield due to the insufficient concentration of
methanol to shift the equilibrium reaction toward completion (Amani et al., 2014).
Moreover, the use of excess methanol also decreases the catalyst activity by getting
bonded to its active sites due to methanol flooding. At the end of the reaction the
process of recovery of the nonreacted methanol requires a substantial amount of
energy that ultimately increases the production cost. Hence, this is not a suggested
step as it results in a wastage of materials. This brings us to the inference that the
use of optimum alcohol is very important to have a higher biodiesel yield.
Converting triglycerides and fatty acids into biodiesel include the usage of catalyst
to speed up the reaction by lowering the activation energy and ultimately affecting the
biodiesel yield. Initially, lower catalyst loading is applied to measure biodiesel conver-
sion. An increase in catalyst loading may leadtodecreaseindiffusion rate of reactants
in bulk mass fraction due to which a decrease in biodiesel yield is observed. However,
in some cases, an increase in water content due to esterification reaction can deactivate
the catalyst, thereby decreasing the final biodiesel yield (Shu et al., 2010).
For the heterogeneous reaction system, the reaction temperature is a crucial
parameter due to the mass transfer limitation at the initial part of the reaction which
is caused by the three immiscible phases of oil, methanol, and solid acid catalyst.
Moreover, raising temperature inclines the equilibrium toward the product for the
reversible and endothermic property of esterification and transesterification reactions.
Nevertheless, the excessive high temperature would aggravate alcohol evaporation
and lead to poor contact with the reaction system by creating one more phase.
It is observed in most of the reactions that there is an increase in biodiesel yield
when there is an increase in reaction time. However, excess reaction time is also con-
sidered as one of the decisive factors, which affects the biodiesel yield efficiency as
well as the cost of energy consumed. It may be due to the deactivation of the active
site of the catalyst during longer reaction time, owing to binding of polar molecule
such as alcohol and water in the reaction mixture and leaching of active sites.