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Aplicações avançadas e estudos de materiais lignocelulósicos para alcançar o modelo de biorrefinaria

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dc.contributor.advisor Colodette, Jorge Luiz Silva, Teresa Cristina Fonseca da 2014-08-20T11:50:04Z 2014-08-20T11:50:04Z 2011-05-06
dc.identifier.citation SILVA, T. C. F. Aplicações avançadas e estudos de materiais lignocelulósicos para alcançar o modelo de biorrefinaria. 2011. 105 f. Tese (Doutorado em Agroquímica). Viçosa: Universidade Federal de Viçosa, 2011. pt_BR
dc.description Tese de Doutorado defendida na Universidade Federal de Viçosa pt_BR
dc.description.abstract pt_BR
dc.description.abstract Cellulose, hemicelluloses and lignin are the three structural components of biomass. They were detailed studied and exploited to achieve the biorefinery model. Cellulose and hemicelluloses were extracted from Eucalyptus urograndis hardwood specimens while lignin was extracted from Eucalyptus urograndis, Eucalyptus globulus, Eucalyptus nitens and Populus trichocarpa specimens. Nanofibrillated cellulose (NFC) was modified with TEMPO and hydroxyapatite (HAp) and then, used to produce cellulose-based aerogels by direct freeze-drying. Oxidized aerogels morphology shows a homogeneous pore size distribution which was maintained after HAp addition. Modified aerogels produced also displayed higher strength than the non- modified one. Xylans polysaccharides were either used as an additive on cellulose pulp and also as basis for production add-value materials - hydrogels. For the primary use, xylans were modified to produce different amounts and types of uronic acids and the effect of the chemical modification, temperature and time of adsorption onto eucalyptus pulp was investigated. Higher temperatures greatly improved adsorption whereas adsorption time had no significant effect on adsorption. Low uronic acid-xylan had greater adsorption on pulp, followed by enriched hexenuronic acid xylan and xylan enriched with methylglucuronic acid groups. Xylans were also used to produce hydrogels in two different ways via radical polymerization: i) Xylan/poly(2- hydroxyethylmethacrylate)-based hydrogels were prepared after crosslinking induced by methacrylic monomers and ii) lignin-carbohydrate complex-based hydrogels using methacrylic monomers. Hydrogels properties could be easily tuned according to the presence acetyl groups and degree of substitution of methacrylate monomers attached to the xylan chain. Acetyl groups introduced compactness and stiffness to the hydrogels which ultimately reduced their water swelling capacity and moreover, enhanced their drug release properties. For the second path, a facile step to form hydrogels by radical polymerization with HEMA was successfully accomplished. The presence of double bonds formed during mild delignification (using peracetic acid) of lignin-carbohydrate complex (LCC) was the reason attributed to the crosslinking. Once again, the presence of acetyl groups in xylan chains played an important role for tuning hydrogel properties. Finally, lignin from kraft liquor was isolated (technical lignin – TL) and its structure was correlated to the pyrolysis energy measured by differential scanning calorimetry (DSC). Negative relationships were found between lignin substructures such as methoxyl groups, syringyl/guaiacyl and aliphatic OHs whereas positive correlation was found between condensed structures and enthalpy values. pt_BR
dc.format 105 páginas pt_BR
dc.language.iso en pt_BR
dc.publisher Universidade Federal de Viçosa pt_BR
dc.subject.classification Ciências Florestais::Tecnologia e utilização de produtos florestais::Energia de biomassa florestal pt_BR
dc.subject.classification Ciências Florestais::Tecnologia e utilização de produtos florestais::Tecnologia de celulose e papel pt_BR
dc.title Aplicações avançadas e estudos de materiais lignocelulósicos para alcançar o modelo de biorrefinaria pt_BR
dc.title Advanced applications and studies of lignocellulosic materials for achieving the biorefinery mode pt_BR
dc.type Tese pt_BR

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