Page 134 - Refining Biomass Residues for Sustainable Energy and Bioproducts

104 Refining Biomass Residues for Sustainable Energy and Bioproducts

utilization of low-quality feedstock like industrial wastes and nonedible oils. The
acid-functionalized support sets the basic platform for the development of low-
value biomass acid catalyst. In order to enhance the acid functionalization in bio-
mass, the polycyclic aromatic carbon sheets with high densities of SO 3 H group
were synthesized with the help of different preparation methods. The following are
the conclusions:
1. The direct sulfonation is a simple, economical, and easy method for preparation of the
catalyst, but the only drawback associated with it is that it fails to produce catalysts with
a high SO 3 H density and porosity simultaneously.
2. Thermal process has high energy cost due to the effect of parameters such as temperature
and time in carbonization and sulfonation process, and it may vary based on their nature
and type of biomass. Lower molecular weight biomass has more rapid and energy effi-
cient process.
3. The hydrothermal process is used to increase uniformity on the surface area with evenly
distributed SO 3 H group that improves the catalytic activity in both esterification and
transesterification process. On the other hand, it leads to the biomass decomposition under
heterogeneous and homogeneous conditions with different routes toward polyaromatic
hydrochar.
4. The solvothermal process helps to improve surface properties for the efficient loading of
the active site thereby adding shorter chain alcohol as solvent that helps to dissolve bio-
mass in a limited heterogeneous route.
5. Catalyst synthesis using special sulfonating agents has high catalytic activity and is easy
to separate when compared to concentrated sulfuric acid because it retains the original
skeleton structure of biomass.
It can be concluded that biomass material might possess an excellent support for
acid catalyst because its structures, stability, textural, and catalytic properties can
be regulated by different preparation methods. It is also observed that the activity
of the catalyst correlated very well with increasing strong acid sites, thereby
increasing the surface area as well as sulfonic acid content. Their properties majorly
depend on the nature of attached molecule or groups with the possibility of being
utilized as heterogeneous catalysts to synthesize biodiesel. These catalysts are also
found to be cleaner and greener than the conventional homogeneous catalysts. A
good reusable nature of the sulfonic acid functionalized biomass catalysts is
observed.

Declaration

The authors did not receive any specific grant from any funding agency.