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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Enhancing Levoglucosan Formation during Fast Pyrolysis of Lignocellulosic Biomass

Li, Qi 15 December 2012 (has links)
Levoglucosan is the major anhydrosugar component of bio-oil produced by fast pyrolysis. Previous research has shown that levoglucosan yield can be greatly increased if a mild acid pretreatment is applied to demineralize the feedstock prior to pyrolysis. The interest in levoglucosan production is that it provides a route to production of monomeric sugars, primarily glucose, which can be utilized to produce biochemically derived fuels (ethanol, butanol, etc.) In one study, four different lignocellulosic biomass were subjected to pyrolysis as feedstocks to produce bio-oils via fast pyrolysis in a 7 kg/h feed rate auger reactor. Feedstocks were pretreated with dilute phosphoric acid and bio-oils were produced and analyzed to compare the bio-oil characteristics from both untreated and treated feedstocks. The results shown in this study strongly indicate that the ash content and alkali metal content are very important parameters which can greatly affect the yield and many properties of bio-oils produced during fast pyrolysis. The dilute acid pretreatment performed in this study significantly reduced the total ash content and alkali metal content in the feedstocks, resulting in a great increase in the bio-oil and levoglucosan yields. It was also shown that dilute acid pretreatment was more effective in treating herbaceous feedstocks than woody biomass in terms of increasing bio-oil production yield and improving bio-oil properties. In one study, bio-oil composed of high levoglucosan concentration was produced via fast pyrolysis of dilute acid pretreated loblolly pine wood in an auger reactor. Water-to-bio-oil ratio, temperature, and time were selected as the three parameters to investigate the optimal condition for extracting the maximum amount of levoglucosan from the bio-oil. The optimal condition for levoglucosan extraction determined was 1.3 : 1 (water-to-bio-oil ratio), 25 oC, and 20 min, producing a levoglucosan yield of 12.7 wt %. The final study developed a new method based on pyrolysis of dilute acid pretreated loblolly pine wood and modification of the pyrolysis process. This new method resulted in a significant 30.7 wt % increase in levoglucosan concentration in the bio-oil organic portion. The results indicated that this method successfully suppressed the levoglucosan decomposition during fast pyrolysis.
2

Controlled Ring Opening Polymerization of 1,2-Anhydrosugars towards Precision Polysaccharides:

Dym, Shoshana M. January 2023 (has links)
Thesis advisor: Jia Niu / Thesis advisor: Jim Morken / Polysaccharides make up one of the largest classes of nature’s macromolecules. However, they are severely understudied relative to other biomolecules such as proteins and DNA sequences. This is because discrete polysaccharides are difficult to isolate from nature or synthesize in laboratories in large enough quantities for thorough research. Polymerization is an efficient route to polysaccharides, yet has historically suffered from harsh conditions and lack of control. Herein, we investigate recent developments in the field of living polymerization as strategies towards synthesis of precision polysaccharides from 1,2- anhydrosugars. We specifically focus on cationic ring opening polymerization (ROP) and reversible addition-fragmentation chain transfer (RAFT) ROP polymerization of 1,2-O-Bn-3,4,6-anhydromannose and 1,2-O-Bn-3,4,6-anhydroglucose. Our research screens various catalyst/initiating systems. Our findings demonstrate that cationic ROP and RAFT polymerization are unsuccessful in the living ROP of 1,2-anhydrosugars. / Thesis (MS) — Boston College, 2023. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

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