274
produce fuels and chemicals. However, since most of these reactions are carried out
in the solvent phase at high temperatures, stability of the catalyst remains a challenge
[8]. Therefore, rational design and development of the catalyst is believed to be a
key factor for determining the success of this sustainable process for which a
complete molecular-level understanding is required.
Experimnetal techniques may provide some insights about the reaction mechanism however they are still insufficient to construct the detailed reaction mechanism
and thus are open to multiple interpretations especially in the field of biomass
upgradation owing to the complexity of catalysts, substrates, and reaction media.
Advances in high-performance computing and computational methods have made
computational design of the catalyst a reality, and the field has reached enough
maturity to ensure that the reactions can be described accurately [9]. Computational
chemistry methods can predict the properties of a chemical system and allow
insights into the reaction that are inaccessible through experiments. These properties
are either accessed through quantum chemical method based on the electronic
structure calculations such as density functional theory (DFT) [10], or classical
force fields to describe the dynamics of atoms with respect to time in the system
without considering the behavior of the electrons such as classical molecular
dynamic simulations (MD) [11]. In order to study the dynamics during chemical
transformations such as bond breaking and formation or charge distribution, ab
initio molecular dynamics (AIMD) [12], Car-Parrinello molecular dynamics
(CPMD) [13], metadynamics (MTD) [14], etc. are used.
Some of the key findings based on molecular modeling-based investigation in the
field of biomass valorization are summarized in this chapter. The chapter first
discusses about the role of computational chemistry in understanding the reaction
mechanism of different reactions that are generally employed in biomass upgradation
which is crucial for the catalyst design. Further, since most of these reactions are
carried out in the presence of solvents, the role of molecular dynamic simulations to
understand the effect of solvents in affecting the reaction mechanism and changing
the yields is discussed. The last section highlights the role of CPMD calculations
combined with metadynamics in revealing the biomass pyrolysis chemistry.
2 Reaction Mechanism
2.1 Acid-Catalyzed Conversion of Carbohydrates
Lignocellulosic biomass comprises of three components: cellulose, hemicellulose,
and lignin [15]. Upon acid-catalyzed hydrolysis, these components yield C6 and C5
sugar monomers such as glucose and xylose [15]. Glucose can be upgraded to a
variety of biofuels and chemicals [16]. Among these chemicals,
5-hydroxymethylfurfural (5-HMF) has emerged as a potential platform molecule
for the production of polymers [17], chemicals, and biofuels [18]. Glucose can
S. Gupta
produce fuels and chemicals. However, since most of these reactions are carried out
in the solvent phase at high temperatures, stability of the catalyst remains a challenge
[8]. Therefore, rational design and development of the catalyst is believed to be a
key factor for determining the success of this sustainable process for which a
complete molecular-level understanding is required.
Experimnetal techniques may provide some insights about the reaction mechanism however they are still insufficient to construct the detailed reaction mechanism
and thus are open to multiple interpretations especially in the field of biomass
upgradation owing to the complexity of catalysts, substrates, and reaction media.
Advances in high-performance computing and computational methods have made
computational design of the catalyst a reality, and the field has reached enough
maturity to ensure that the reactions can be described accurately [9]. Computational
chemistry methods can predict the properties of a chemical system and allow
insights into the reaction that are inaccessible through experiments. These properties
are either accessed through quantum chemical method based on the electronic
structure calculations such as density functional theory (DFT) [10], or classical
force fields to describe the dynamics of atoms with respect to time in the system
without considering the behavior of the electrons such as classical molecular
dynamic simulations (MD) [11]. In order to study the dynamics during chemical
transformations such as bond breaking and formation or charge distribution, ab
initio molecular dynamics (AIMD) [12], Car-Parrinello molecular dynamics
(CPMD) [13], metadynamics (MTD) [14], etc. are used.
Some of the key findings based on molecular modeling-based investigation in the
field of biomass valorization are summarized in this chapter. The chapter first
discusses about the role of computational chemistry in understanding the reaction
mechanism of different reactions that are generally employed in biomass upgradation
which is crucial for the catalyst design. Further, since most of these reactions are
carried out in the presence of solvents, the role of molecular dynamic simulations to
understand the effect of solvents in affecting the reaction mechanism and changing
the yields is discussed. The last section highlights the role of CPMD calculations
combined with metadynamics in revealing the biomass pyrolysis chemistry.
2 Reaction Mechanism
2.1 Acid-Catalyzed Conversion of Carbohydrates
Lignocellulosic biomass comprises of three components: cellulose, hemicellulose,
and lignin [15]. Upon acid-catalyzed hydrolysis, these components yield C6 and C5
sugar monomers such as glucose and xylose [15]. Glucose can be upgraded to a
variety of biofuels and chemicals [16]. Among these chemicals,
5-hydroxymethylfurfural (5-HMF) has emerged as a potential platform molecule
for the production of polymers [17], chemicals, and biofuels [18]. Glucose can
S. Gupta