252
bagasse) can be obtained by various carbonization techniques such as pyrolysis,
gasification, hydrothermal carbonization, etc. Sometimes, the carbon-based functionalized catalysts are prepared from municipal waste, complex industrial sludge,
etc. This approach of converting biomass and waste into catalysts can benefit in two
ways; the first one is the reduced cost of material fabrication, and the second one is
the reduction in environmental pollution by utilizing waste. The properties of carbon material (surface area, pore configuration) are highly influenced by activation
techniques and other key parameters such as source material, type of activation
agent, time, and temperature [43].
Carbon material acts as excellent support for active catalyst phases. One such
example is ionic liquids (ILs) supported on the carbon-based sulfonated catalyst. A
high yield (47–65%) of 5-hydroxymethylfurfural was obtained when inulin was
reacted at 100
o
C for 60 min using ILs supported on carbon material. The catalyst
performed well compared to conventional solid acid catalysts with high reusability.
The carbon-based catalysts are expected to perform at par with their conventional
counterparts. To verify this, four amorphous carbon-based sulfonated catalysts were
prepared from d-xylose, cellulose, lignin, cellulose, and wood and compared with
cation resin, HZSM-5, sulfated zirconia, and Amberlyst-15. All four carbon-based
catalysts showed comparable catalytic activity over the conventional solid acid
catalysts [44]. In another study, a carbon catalyst prepared via hydrothermal
carbonization of water hyacinth was used for oleic acid esterification and also for
xylose dehydration to furfural. The solid acid bearing the highest acidity
(WH-PTSA-220) showed maximum catalyst activity, whereas catalyst prepared
with high temperature (WH-PTSA-240) had shown favorable reusability due to
enhance graphitization and hydrophobicity of the carbon surface [45]. The one-pot
catalytic synthesis, developed by the Sels group, converts crystalline cellulose into
simple alkanes using a modified Ru/C catalyst [46]. A series of bimetallic
nanocatalysts supported on carbon (PtMn/C, PtFe/C, PtNi/C, PtZn/C, etc.) are
reported to be used for the efficient oxidative conversion of glycerol to glyceric
acid. Ninety-one percent of glycerol was converted within 8 h at 60 °C, with a 50%
yield of glyceric acid. Carbon support is chosen because of its inert behavior in
acidic environment [47].
Graphene-Based Catalysts
The advancement in graphene-based catalysts has paved a new way for its application in biomass processing. Graphene, along with graphene oxide (GO) and reduced
graphene oxide (rGO), is increasingly used for biomass conversion. Graphene oxide
is synthesized by oxidation of graphite, and reduced graphene oxide is synthesized
by reduction of graphene oxide. Graphene per se has limited catalyst activity, which
can be enhanced by the doping of heteroatoms such as nitrogen, boron, or sulfur.
Graphene-based supports can be synthesized from biomass, and biomass-derived
chemicals, for example, glucose to graphene [48]. It also facilitates the anchoring of
various acid-base functionalities and metal nanoparticles (NPs). Graphene-based
R. Bhoi et al.
bagasse) can be obtained by various carbonization techniques such as pyrolysis,
gasification, hydrothermal carbonization, etc. Sometimes, the carbon-based functionalized catalysts are prepared from municipal waste, complex industrial sludge,
etc. This approach of converting biomass and waste into catalysts can benefit in two
ways; the first one is the reduced cost of material fabrication, and the second one is
the reduction in environmental pollution by utilizing waste. The properties of carbon material (surface area, pore configuration) are highly influenced by activation
techniques and other key parameters such as source material, type of activation
agent, time, and temperature [43].
Carbon material acts as excellent support for active catalyst phases. One such
example is ionic liquids (ILs) supported on the carbon-based sulfonated catalyst. A
high yield (47–65%) of 5-hydroxymethylfurfural was obtained when inulin was
reacted at 100
o
C for 60 min using ILs supported on carbon material. The catalyst
performed well compared to conventional solid acid catalysts with high reusability.
The carbon-based catalysts are expected to perform at par with their conventional
counterparts. To verify this, four amorphous carbon-based sulfonated catalysts were
prepared from d-xylose, cellulose, lignin, cellulose, and wood and compared with
cation resin, HZSM-5, sulfated zirconia, and Amberlyst-15. All four carbon-based
catalysts showed comparable catalytic activity over the conventional solid acid
catalysts [44]. In another study, a carbon catalyst prepared via hydrothermal
carbonization of water hyacinth was used for oleic acid esterification and also for
xylose dehydration to furfural. The solid acid bearing the highest acidity
(WH-PTSA-220) showed maximum catalyst activity, whereas catalyst prepared
with high temperature (WH-PTSA-240) had shown favorable reusability due to
enhance graphitization and hydrophobicity of the carbon surface [45]. The one-pot
catalytic synthesis, developed by the Sels group, converts crystalline cellulose into
simple alkanes using a modified Ru/C catalyst [46]. A series of bimetallic
nanocatalysts supported on carbon (PtMn/C, PtFe/C, PtNi/C, PtZn/C, etc.) are
reported to be used for the efficient oxidative conversion of glycerol to glyceric
acid. Ninety-one percent of glycerol was converted within 8 h at 60 °C, with a 50%
yield of glyceric acid. Carbon support is chosen because of its inert behavior in
acidic environment [47].
Graphene-Based Catalysts
The advancement in graphene-based catalysts has paved a new way for its application in biomass processing. Graphene, along with graphene oxide (GO) and reduced
graphene oxide (rGO), is increasingly used for biomass conversion. Graphene oxide
is synthesized by oxidation of graphite, and reduced graphene oxide is synthesized
by reduction of graphene oxide. Graphene per se has limited catalyst activity, which
can be enhanced by the doping of heteroatoms such as nitrogen, boron, or sulfur.
Graphene-based supports can be synthesized from biomass, and biomass-derived
chemicals, for example, glucose to graphene [48]. It also facilitates the anchoring of
various acid-base functionalities and metal nanoparticles (NPs). Graphene-based
R. Bhoi et al.