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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.
71

The distribution and behaviour of lignin in the estuarine environment

Reeves, Alison Dawn January 1988 (has links)
No description available.
72

Towards the synthesis of model peroxidases

Varejao, Jorge Manuel Tavares Branco January 2000 (has links)
No description available.
73

Synthesis of polyurethane from one hundred percent sustainable natural materials through non-isocyanate reactions

Lee, Albert 12 January 2015 (has links)
The synthesis route for the preparation of polyurethane using 100% sustainable materials was proposed. Lignin, one of the most abundance biomass on Earth, was used as one raw material, while the other one used is soybean oil. The reaction occurs in 3 steps, and is done in 2 different pot reactions. Briefly, purchased epoxidized soybean oil is carbonated to synthesize carbonated soybean oil. Then carbonated soybean oil was reacted with coupling agent, 3-aminopropyltriethoxysilane to produce urethane monomers. Finally, prepared urethane monomers were polymerized with lignin to produce sustainable polyurethane. Molecular structures were intensively analyzed using Fourier-Transform Infrared Spectroscopy and Nuclear Magnetic Resonance Spectroscopy. In addition, mechanical properties of prepared polyurethane were analyzed in order to evaluate its performance and compare with the polyurethanes available commercially. Our results indicated that the highest tensile strength achieved was 1.4 MPa, which is slightly below the typical tensile strengths of processible polyurethane. Chemical properties of all the intermediates and products and implications for future research are discussed.
74

Aqueous phase processing of lignocellulosic biomass for biofuel production

Mu, Wei 12 January 2015 (has links)
This thesis studied the catalytic upgrading of pyrolysis oil derived from both ethanol organosolv (EOL) lignin and whole biomass. There are four major components of this thesis. In the first part, several lignin model compounds and the commonly used noble metal catalysts were evaluated. During the reaction, coke formation deactivated several catalysts. The reaction pathway of the coke formation was proposed. Ruthenium/activated carbon can hydrogenate the aromatic ring and remove the methoxyl group as well due to its unique catalytic behavior. The reaction mechanism was deduced based on the products distribution of the model compounds. The second part of this study focuses on the catalytic HDO reaction with real EOL pyrolysis oil. The results indicate the reaction mechanism with EOL pyrolysis oil is similar to the results of the model compound study. Due to the deactivation of the Ru/C catalyst by tar produced during the upgrading, two-step hydrodeoxygenation at different temperature was adopted in this study. The second part mainly discussed the first-step HDO reaction. The upgraded pyrolysis oil was analyzed using GC-MS, ¹H, ¹³C, and HSQC ²D NMR. The chemical structure change after the first-step upgrading and the cleavage of the inter-linkages were included. The third part focuses on the product analysis after the second-step HDO. All the products were completely hydrogenated. The molecular weight of the upgraded oil is in the monomer range and the GC-MS study provided detailed compound structures. However, some of them still contain oxygen atoms. To produce completely deoxygenated products, alkali treated ZSM-5 was used as a supporting material and it was effective in catalyzing the dehydration reaction and producing deoxygenated compounds. In the fourth part, light oil derived from whole biomass also underwent treatment under the same HDO reaction conditions as those used in upgrading EOL pyrolysis oil. In this reaction, the biomass were separated into three components: stem, residue and bark. The compound structures of the three different types of light oil were analyzed by GC, ¹H and ¹H-¹³C HSQC-NMR. Then the light oil was processed under the same condition as the heavy oil upgrading. The reaction mechanisms with cellulose and hemicellulose were also studied. These results will be of value in developing of complete hydrogenation of whole biomass pyrolysis oils.
75

The leaching of lignin macromolecules from pulp fibres during washing /

Favis, Basil D. January 1981 (has links)
A method was developed for measuring the rate of leaching of lignin macromolecules from the fibre walls of unbleached kraft pulp fibres suspended in water. From a comparison of a theoretical analysis with experimental results, it was concluded that the leaching process was governed by a diffusion mechanism. Very low and widely polydisperse diffusion coefficients were observed for this system. The molecular weights of the leached lignins were found to increase with wash time. A comparison of the molecular dimensions with pore size indicated that a flat disk-like conformation, rather than a spherical conformation was appropriate for the lignin macromolecule. From 20(DEGREES) C to 70(DEGREES)C the change in the intrafibre diffusion coefficient with temperature varied directly as the ratio of the absolute temperature to the viscosity of water. Above 70(DEGREES)C there was a much larger dependence of the diffusion coefficient on temperature. The rate of leaching was also affected by the presence of electrolytes in the wash liquid; leaching was found to decrease with an increase in the ionic strength of the electrolyte. A conceptual model for this leaching effect is presented. The model offers a qualitative explanation for the experimental results noted above.
76

The topochemistry of delignification reactions.

Wood, John Russell. January 1972 (has links)
No description available.
77

The distribution of lignin in aspen wood.

Musha, Yoshinori. January 1970 (has links)
No description available.
78

Physico-chemical mechanisms of delignification

Kerr, Allan J. January 1974 (has links)
No description available.
79

Organic chemistry of bark phenolic acid

Fahey, Michael Duncan 02 November 1956 (has links)
Graduation date: 1957
80

Mating system and DNA transformation of the lignin-dagrading basidiomycete Phanerochaete chrysosporium /

Alic, Margaret. January 1990 (has links)
Thesis (Ph. D.)--Oregon Graduate Institute of Science and Technology, 1990.

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