resumo
Technical hydrolysis lignin (THL) was micronized by grinding in a rotary-jet mill to obtain a fraction of approximately 5 mm. Both initial and milled THLs were liquefied by thermal alkaline treatment at 220 degrees C for 2 h. Upgraded THLs that were nonmilled (L1) and milled (L2) were desalted by treatment with cation-exchanged resin and were dried. Micronization affected the course of hydrothermal alkaline treatment and the structure and composition of the obtained lignin. Thus, L2 contained much less concomitant polysaccharides and extractives than L1 and was more condensed. The molecular weights of L1 and L2 were 1100 and 1000 Da, respectively, as determined by size-exclusion chromatography. Structural characterization carried out by employing tandem electrospray ionization-mass spectrometry and 1D and 2D nuclear magnetic resonance spectroscopy revealed that small amounts of beta-O-4 (similar to 6 mol.%), beta-5, and beta-beta structures still remained in L1 and L2. Overall, upgraded lignins are oligomers (trimers--pentamers) with highly degraded propane chains and possess polyconjugated condensed aromatic structures. Upgraded THL seems to be a promising raw material for polymeric formulations.
palavras-chave
TECHNICAL LIGNINS; PRODUCTS; EXTRACTION; WOOD
categoria
Forestry; Materials Science
autores
Krutov, SM; Evtuguin, DV; Ipatova, EV; Santos, SAO; Sazanov, YN
nossos autores
Dmitry Evtyugin
Professor Associado com Agregação
Sónia Andreia Oliveira Santos
Investigador Auxiliaragradecimentos
This work was carried out under the financial support provided by RSF grant no. 14-13-00448. The authors also thank the CICECO for the financing of this study within the scope of the FCT grant PEst-C/QUI/UI0062/2013. The authors are grateful to Prof. A.V. Pranovich (Laboratory of Wood and Paper Chemistry, angstrom bo Akademi University) and I.V. Sumerskiy (University of Natural Resources and Life Sciences, Vienna) for their technical contribution in this work.