Dissertation
Theoretical study of biomass pretreatment processes kinetic, computational fluid dynamics, molecular dynamics and quantum mechanical modelling
Doctor of Philosophy (PhD), Washington State University
01/2017
Handle:
https://hdl.handle.net/2376/111891
Abstract
This thesis introduces interdisciplinary strategies used to study pretreatment techniques that include computational fluid dynamics, kinetics, quantum mechanics and molecular dynamics. The First and second chapters review the pretreatment techniques and computational methods. The third chapter describes a computational fluid dynamics (CFD) and kinetic study of the ozone pretreatment of wheat straw, including experimental validation. A kinetic model based upon a “cuticle hypothesis” was developed to fit the lignin concentration. The results indicate that parameters derived from a cuticle-based model provide a better fit to experimental results compared to a model without a cuticle layer. In the fourth chapter, the energetics and kinetics of hydroxyl radical (OH●) addition reactions to β-O-4 type lignin molecules was studied along with the subsequent dissociation of the C-O bond within β-O-4 linkage using G4MP2 method. The results demonstrate that the OH● addition reaction is both kinetically and energetically favored. However, OH● addition increases the BDE of β-O-4 linkages by 10 to 20 kcal/mol compared to lignin. In chapter 5, the ring hydroxylation reactions of β-O-4 lignin molecule in the presence of molecular oxygen and OH● are studied by using quantum mechanical methods. A three steps ring hydroxylation mechanism of β-O-4 lignin molecules is proposed and the energy of the reactants and products structure and C-O BDE were calculated using G4MP2 theory. Ring hydroxylation mechanism is predicted to be energetically favored. Further, BDE of β-O-4 linkages of the hydroxylated lignin decreased by10 to 20 kcal/mol. The results revealed that ring hydroxylation reactions may be important in termite pretreatment to alter the β-O-4 C-O BDE. The sixth chapter discusses the application of the ReaxFF force field implemented in classical molecular dynamics simulations for studying the reactivity of OH● and phenol and β-O-4 lignin molecules in bulk water. ReaxFF is able to predict that the ortho addition of OH● to phenol and C1 addition to lignin are the predominant reactions. ReaxFF can reliably predict OH● addition reactions to phenol and lignin molecules giving us confidence in future ReaxFF simulations of a broader range of substrates.
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Details
- Title
- Theoretical study of biomass pretreatment processes kinetic, computational fluid dynamics, molecular dynamics and quantum mechanical modelling
- Creators
- Sujala Bhattarai
- Contributors
- Aurora E Clark (Advisor)Shulin Chen (Advisor)Cornelius F Ivory (Committee Member)Kirk Peterson (Committee Member)Garcia-P'erez Manuel (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Biological Systems Engineering
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 171
- Identifiers
- 99900581826601842
- Language
- English
- Resource Type
- Dissertation