CIMO - Artigos em Proceedings Não Indexados à WoS/Scopus
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Browsing CIMO - Artigos em Proceedings Não Indexados à WoS/Scopus by Subject "Acetylation"
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- FTIR and NMR studies on lignin acetylationPublication . Cateto, Carolina; Barreiro, M.F.; Rodrigues, Alírio; Brochier-Salon, M.C.; Thielemans, Wim; Belgacem, Mohamed NaceurIn this work, a comparative study of an acetylation procedure, using four different lignin samples was performed. The chosen lignin samples, Indulin AT (Meadwestvaco), Alcell (Repap), Curan 27-11P (Borregaard LignoTech) and Sarkanda (Granit SA), represent both the guaiacyl and guaiacyl-syringyl type, and were obtained from different pulp processes (kraft and organosolv). Lignin was acetylated using an acetic anhydride-pyridine mixture and the final sample was recovered by precipitation. Final samples, with different reaction times (1 and 2 hours), were characterized by FTIR and 13C NMR analysis, and the obtained spectra were compared with the corresponding ones for non-acetylated samples. Within the used experimental conditions and samples, an incomplete acetylation yield appeared to be common. Total hydroxyl content, determined independently by titration and based on the 13C NMR results, was found to be in close agreement.
- Lignin characterization by acetylation proceduresPublication . Cateto, Carolina; Rodrigues, Alírio; Barreiro, M.F.The amount of the total hydroxyl content of lignin is of great importance in the formulation of a lignin based polyurethane system since it allows the quantity of the polyisocyanate counterpart within the right stoichiometry. In this work, the reliability of an acetylation procedure, regarding the determination of total hydroxyl content of a commercial kraft lignin, was studied. Lignin was acetylated using acetic anhydride reagent in solution in pyridine and the recovered acetylated samples were analysed by FTIR using KBr pellets. The experimental variables investigated were: reaction time, reaction temperature, composition of the acetylation reagent, presence of a catalyst and drying process of the acetylated samples. Within this work, the obtained results indicate that acetylation was incomplete for all the studied conditions, resulting in an unreliable total hydroxyl determination and shows the limitation of this technique. This observation is in accordance with recent published works (see, for example, Gosselink et al., 2004) and could justify the lack of agreement among some published experimental results concerning interlaboratory analysis.