Patricia Soares Bilhalva dos Santos

Composition and structure of organosolv lignins from four eucalypt species

Lignins were extracted from different species using organosolv process (ethanol/water). Obtained organosolv lignins were characterised by various methods to determine their composition, structure and functional groups with the purpose of evaluating their potential use for obtaining value-added compounds. The purity of organosolv lignins was determined. The total phenols content and the antioxidant power were analysed in order to know the reactivity of lignins. The ratio S/G was determined by nitrobenzene oxidation. In addition, molecular weight distribution, infrared spectroscopy and thermo gravimetrical analysis were carried out in order to determine the physical and chemical properties of organosolv lignins. Obtained organosolv lignins have very high purity and low sugar and inorganic contamination. All organosolv lignins samples have high polydispersity, and lignin from grey ironbark wood had the highest molecular weight average. Among the organosolv lignins, lemon-scented gum showed the highest average value of S/G ratio and the lowest average value of total phenols.

Kraft Lignin-Based Polyols by Microwave: Optimizing Reaction Conditions

Microwave liquefaction of precipitated Kraft lignin was carried out in polyethylene glycol (PEG) and glycerol (G) mixed with or without H2SO4 as catalyst. The influences of some independent variables on the yield and hydroxyl index were discussed. The viscosity, molecular distribution (GPC), and the types of volatiles measured by gas chromatography–Mass spectrometry (GC-MS) of all the liquefied products were determined. Response surface methodology (RSM) was used to optimize liquefaction conditions. Based on the results, lignin/solvents (wt%), catalyst/solvents (wt%), and reaction time were chosen as independent variables for a central composite design (CCD). The optimal liquefaction conditions were as: 20 wt% of lignin, 3 wt% of catalyst at 5 min with yield and hydroxyl number of 95.27% and 537.95 mg KOH.g−1, respectively. Functional groups (measured by ATR-IR [attenuated total reflectance – infrared]) and the thermal degradation (TGA) of optimized bio-polyol and precipitated kraft lignin were determined.

Wood under fresh water: Effect on the chemical properties and on decay resistance

This study aimed to evaluate the effect of waterlogging on the chemical properties and on decay resistance of two fast-growing eucalypt species. Samples of spotted gum and rose gum wood were placed underwater and taken out at different times: after 4, 8 and 12 months. Chemical properties were performed via wet chemical quantification (Tappi standards), monomeric sugars by HPLC, and qualitative evaluation of extractives by Py-GC/MS and ATR-IR spectroscopy; biological performance was investigated using Trametes versicolor and Gloeophyllum trabeum rot fungi. The results showed slight changes to the chemical properties of both wood species, with an increase in lignin represented by the reduction of sugars due to waterlogging. Both species showed higher susceptibility to Gloeophyllum trabeum mainly in the sapwood, with no influence on decay resistance due the waterlogging.

Efeito dos extrativos no inchamento das madeiras de Eucalyptus grandis e Corymbia citriodora

O presente estudo teve como objetivo avaliar o efeito dos extrativos no inchamento das madeiras de Eucalyptus grandis e Corymbia citriodora . Para tal, foram utilizadas 30 pecas cubicas de 20 x 20 x 20 mm. Deste modo, foram realizadas extracoes em etanol em dez amostras, extracao em agua quente em outras dez amostras e as demais foram utilizadas como testemunhas (amostras sem extracao). Apos secagem a 60°C em estufa ate massa constante, todas as madeiras foram imersas em agua destilada para avaliacao do inchamento linear (radial e tangencial) e volumetrico apos 2, 12, 24 e 48 horas. Os resultados obtidos denotam que o inchamento da madeira de Corymbia citriodora deu-se em maior proporcao apos extracao em etanol. Nao observou-se grande variacao entre os resultados obtidos para as amostras testemunhas e as submetidas a extracao em agua quente. De maneira geral, verificou-se aumento gradual do inchamento ao longo do tempo para a madeira de Corymbia citriodora . Ja para a madeira de Eucalyptus grandis , o inchamento apresentou uma estabilizacao apos um periodo de 24 horas. Para esta especie, o inchamento volumetrico foi superior para as pecas submetidas a extracao em etanol. Os extrativos influenciaram no inchamento linear e volumetrico das madeiras das duas especies estudadas. No entanto, a polaridade dos solventes deve ser levada em conta.