94
A. R. Abouelela et al.
5.3 Technology Concept Formulated (TRL 2-3)
The natural high recalcitrance of wood and its insolubility in common solvents has
severely hindered the development and the utilization of lignocellulosic biomass as a
feedstock for biofuels and biochemicals production. The ability to solubilize cellulose
in common imidazolium-based ILs was the gateway towards investigating the use
of ILs as a pretreatment medium to deconstruct the biopolymers of lignocellulosic
biomass [66]. Ionic liquids’ structural variability and designer properties inspired
scientists to use ILs to overcome the challenges faced in conventional pretreatment
processes, such as solvent losses, high-pressure operation, waste generation, and
sugar degradation [67–69].
5.3.1 Biomass Pretreatment Using Ionic Liquids
In 2007, Rogers et al. explored the use of ILs to extract cellulose from a variety of
hardwood and softwood lignocellulosic feedstocks. It was found that [C 4 C 1 im][Cl]
was able to partially dissolve the woody material [16]. Cellulose was recovered by
adding an antisolvent (1:1 acetone–water, dichloromethane, or acetonitrile) and the
properties of the reconstituted cellulose were found to be very similar to the properties
of pure cellulose subjected to the same process. In the same year, Kilpeläinen et al.
[70] published a study to investigate the use of several imidazolium-based ILs with
chloride anions in dissolving hardwood and softwood feedstocks. They found that
the solubilization efficiency and dissolution profiles are highly affected by the wood
particle size. The addition of water as an antisolvent recovered an amorphous material
that was a mixture of the wood components. The intriguing nature of the amorphous
material led to investigating its enzymatic digestibility, and they found that 60% of
the theoretical amount of glucose was released versus only 12% released from the
untreated control. Even though the solubility of the lignocellulosic materials did not
exceed 10 wt%, these early studies established the foundation of a new research field
using ionic liquids as a novel platform for lignocellulosic biomass processing.
In the past decade, two IL-based pretreatment approaches were developed: (1)
biomass dissolution processes (non-selective solubilization of the biomass components) and (2) fractionation processes (selective solubilization of lignin and hemicellulose). Each approach uses ionic liquids that interact differently with lignocellulosic
biomass biopolymers [71].
5.3.2 Biomass Dissolution
The biomass dissolution process uses ILs that are capable of dissolving the entire
lignocellulosic biomass components, specifically cellulose, by disturbing its inter-
A. R. Abouelela et al.
5.3 Technology Concept Formulated (TRL 2-3)
The natural high recalcitrance of wood and its insolubility in common solvents has
severely hindered the development and the utilization of lignocellulosic biomass as a
feedstock for biofuels and biochemicals production. The ability to solubilize cellulose
in common imidazolium-based ILs was the gateway towards investigating the use
of ILs as a pretreatment medium to deconstruct the biopolymers of lignocellulosic
biomass [66]. Ionic liquids’ structural variability and designer properties inspired
scientists to use ILs to overcome the challenges faced in conventional pretreatment
processes, such as solvent losses, high-pressure operation, waste generation, and
sugar degradation [67–69].
5.3.1 Biomass Pretreatment Using Ionic Liquids
In 2007, Rogers et al. explored the use of ILs to extract cellulose from a variety of
hardwood and softwood lignocellulosic feedstocks. It was found that [C 4 C 1 im][Cl]
was able to partially dissolve the woody material [16]. Cellulose was recovered by
adding an antisolvent (1:1 acetone–water, dichloromethane, or acetonitrile) and the
properties of the reconstituted cellulose were found to be very similar to the properties
of pure cellulose subjected to the same process. In the same year, Kilpeläinen et al.
[70] published a study to investigate the use of several imidazolium-based ILs with
chloride anions in dissolving hardwood and softwood feedstocks. They found that
the solubilization efficiency and dissolution profiles are highly affected by the wood
particle size. The addition of water as an antisolvent recovered an amorphous material
that was a mixture of the wood components. The intriguing nature of the amorphous
material led to investigating its enzymatic digestibility, and they found that 60% of
the theoretical amount of glucose was released versus only 12% released from the
untreated control. Even though the solubility of the lignocellulosic materials did not
exceed 10 wt%, these early studies established the foundation of a new research field
using ionic liquids as a novel platform for lignocellulosic biomass processing.
In the past decade, two IL-based pretreatment approaches were developed: (1)
biomass dissolution processes (non-selective solubilization of the biomass components) and (2) fractionation processes (selective solubilization of lignin and hemicellulose). Each approach uses ionic liquids that interact differently with lignocellulosic
biomass biopolymers [71].
5.3.2 Biomass Dissolution
The biomass dissolution process uses ILs that are capable of dissolving the entire
lignocellulosic biomass components, specifically cellulose, by disturbing its inter-