Dissertation
INVESTIGATING THE USE OF LIGNIN AND BLOCK COPOLYMERS AS SELF-ASSEMBLING NANOREACTORS IN EFFLUENT
Doctor of Philosophy (PhD), Washington State University
01/2016
Handle:
https://hdl.handle.net/2376/111251
Abstract
The delignification processes allows for the conversion of lignocellulosic biomass into delignified cellulosic fibers and process effluent. Process effluent is laden with lignin-based phenolic compounds derived from lignocellulosics cell walls. The structural heterogeneity of lignin makes it difficult to break down and isolate into a value-added product. It is therefore necessary to identify new chemical transformations that can proceed with high efficiency and selectivity on a complex starting material. It was hypothesized in this work that selective oxidation of either alcohol (secondary and primary) in the diol fragment guaiacylglycerol-β-guaiacyl ether (as one of the most common structures in lignin) could provide a starting structure for the production of low molecular weight aromatics from lignin, presumably by increasing cleavage of the β-O-4 linkage.
Hence, in this work, we first explored the structure of lignin obtained from effluent produced by the sequential ozone and soaking ammonia pretreatment of wheat straw. Then we investigated the formation of block copolymer PEO-PPO-PEO micelles in the aqueous environment of process effluent. We also explored their ability to solubilize guest molecules, including lignin fragments from process streams. The study elucidated the interactions between host micelles and guest compounds. These interactions represent a preferred molecular orientation in self-assembled nanostructures, in which aerobic oxidation of vicinal alcohols can be performed selectively.
The structural characterization reveals that isolated lignin is a H-G-S lignin with an S/G ratio of 0.35, along with low molecular weight compounds derived from hydroxycinnamic acid and G-lignin units. It was found that micelle-lignin interactions and steric rearrangement of solubilize (guest) in the micelles (host) depend on both chemical functional group characteristics of solubilize and π-π interactions between aromatic/conjugated groups. Hereupon, a micellar catalytic system consists of TEMPO/Cu (II), mediated by O2 for chemoselective aerobic oxidation of primary alcohol in the diol fragment guaiacylglycerol-β-guaiacyl ether was studied. The preliminary results highlight the prospect of combining this method with a PEO-PPO-PEO micellar system in the basic condition to achieve the oxidation of primary alcohol to aldehyde.
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Details
- Title
- INVESTIGATING THE USE OF LIGNIN AND BLOCK COPOLYMERS AS SELF-ASSEMBLING NANOREACTORS IN EFFLUENT
- Creators
- Mohammadali Azadfar
- Contributors
- Shulin Chen (Advisor)Manuel Garcia-Perez (Committee Member)Hanwu Lei (Committee Member)Armando G McDonald (Committee Member)Bin Yang (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Biological Systems Engineering, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 151
- Identifiers
- 99900581723201842
- Language
- English
- Resource Type
- Dissertation