250
carried out at mild reaction conditions (temperature 60–70 °C, atmospheric
pressure), whereas heterogeneous catalyst reactions are performed at higher
temperatures (100–180 °C) and pressures (20–40 bar).
The non-edible biomass, i.e., all plant-based residues, are converted to syngas or
bio-oil through thermochemical routes. The biodiesel synthesis from non-edible
and waste cooking oils is gaining momentum as these oils are available at a cheaper
rate and do not have competing usage. Vegetable oil and bio-oil can also be converted
to biogasoline via catalytic cracking but require proper catalyst and reactor setup.
The product of cracking comprises an organic liquid, gas, coke, and some amount
of water. The organic liquid is a mixture of hydrocarbons having properties similar
to gasoline, kerosene, and diesel fractions. The catalysts used for catalytic cracking
of oil include alumina, silica (SBA-15), zeolites (HZSM-5), and silica-alumina
[34]. For example, a fixed bed reactor was used for catalytic cracking of canola oil
to biogasoline over a variety of zeolites under different reaction conditions. Among
the various zeolites used, HZSM-5 was found to be the most effective catalyst with
a 100% conversion of canola oil. The reaction was carried over a temperature range
of 573–773 K. The reaction product contained a high yield of aromatic compounds [35].
Several carbon-based catalysts (multiwalled carbon nanotubes, CNT-P-SO 3 H)
have shown excellent performance for the transesterification of oils and fats. Apart
from thermochemical routes, the non-edible biomass is converted to valuable products/platform chemicals via a catalytic process such as hydrolysis, solvolysis, etc. The
platform chemicals obtained are further converted to valuable products through isomerization, dehydration, hydrodeoxygenation, hydrogenolysis, etc. The various microporous, mesoporous, and nanoparticle catalysts are presented in Table 1.
2.3 Functionalized Heterogeneous Catalyst
Heterogeneous catalysts are preferable over homogeneous ones due to the ease of
separation, reusability, tolerance to moisture, and thermal stability. To make the
biomass conversion process more energy efficient, multifunctional catalysts can
play a major role with an adequate amount of acid, base, and redox-active sites.
Various multifunctional catalysts are discussed in the following section
accommodating such features and can be applied to biomass conversion. The
multifunctional catalyst can reduce few energy-intensive steps in the overall process,
thereby improving the process efficiency.
2.3.1 Carbon-Based Catalysts
Carbon material catalysts have a high surface area, tailorable porosity, and higher
hydrophobicity. These properties make them suitable catalysts for biomass
valorization. They can act as support as well as active phase catalyst. However, the
R. Bhoi et al.
carried out at mild reaction conditions (temperature 60–70 °C, atmospheric
pressure), whereas heterogeneous catalyst reactions are performed at higher
temperatures (100–180 °C) and pressures (20–40 bar).
The non-edible biomass, i.e., all plant-based residues, are converted to syngas or
bio-oil through thermochemical routes. The biodiesel synthesis from non-edible
and waste cooking oils is gaining momentum as these oils are available at a cheaper
rate and do not have competing usage. Vegetable oil and bio-oil can also be converted
to biogasoline via catalytic cracking but require proper catalyst and reactor setup.
The product of cracking comprises an organic liquid, gas, coke, and some amount
of water. The organic liquid is a mixture of hydrocarbons having properties similar
to gasoline, kerosene, and diesel fractions. The catalysts used for catalytic cracking
of oil include alumina, silica (SBA-15), zeolites (HZSM-5), and silica-alumina
[34]. For example, a fixed bed reactor was used for catalytic cracking of canola oil
to biogasoline over a variety of zeolites under different reaction conditions. Among
the various zeolites used, HZSM-5 was found to be the most effective catalyst with
a 100% conversion of canola oil. The reaction was carried over a temperature range
of 573–773 K. The reaction product contained a high yield of aromatic compounds [35].
Several carbon-based catalysts (multiwalled carbon nanotubes, CNT-P-SO 3 H)
have shown excellent performance for the transesterification of oils and fats. Apart
from thermochemical routes, the non-edible biomass is converted to valuable products/platform chemicals via a catalytic process such as hydrolysis, solvolysis, etc. The
platform chemicals obtained are further converted to valuable products through isomerization, dehydration, hydrodeoxygenation, hydrogenolysis, etc. The various microporous, mesoporous, and nanoparticle catalysts are presented in Table 1.
2.3 Functionalized Heterogeneous Catalyst
Heterogeneous catalysts are preferable over homogeneous ones due to the ease of
separation, reusability, tolerance to moisture, and thermal stability. To make the
biomass conversion process more energy efficient, multifunctional catalysts can
play a major role with an adequate amount of acid, base, and redox-active sites.
Various multifunctional catalysts are discussed in the following section
accommodating such features and can be applied to biomass conversion. The
multifunctional catalyst can reduce few energy-intensive steps in the overall process,
thereby improving the process efficiency.
2.3.1 Carbon-Based Catalysts
Carbon material catalysts have a high surface area, tailorable porosity, and higher
hydrophobicity. These properties make them suitable catalysts for biomass
valorization. They can act as support as well as active phase catalyst. However, the
R. Bhoi et al.