Effect of different catalysts on the oxyalkylation of eucalyptus Lignoboost (R) kraft lignin
authors Vieira, FR; Barros-Timmons, A; Evtuguin, DV; Pinto, PCR
nationality International
journal HOLZFORSCHUNG
author keywords bio-based polyols; Lignoboost (R) lignin; organocatalysts; oxyalkylation; propylene carbonate
keywords RING-OPENING POLYMERIZATION; PROPYLENE CARBONATE; CYCLIC CARBONATES; OXYPROPYLATION; POLYOLS; XYLAN
abstract Lignin obtained by Lignoboost (R) procedure from black liquor after kraft pulping of Eucalyptus globulus wood was characterized and converted into liquid polyols via an innovative and safe procedure using base catalyzed oxyalkylation with propylene carbonate (PC). The effect of four catalysts, Potassium carbonate (K2CO3), 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU), dicyanodiamide (DICY), and 1,4-diazabicyclo [2.2.2] octane (DABCO) was evaluated in terms of lignin polyol yield and weight gain. The ensuing polyols were also characterized by fourier transform infrared (FTIR), H-1 NMR, C-13 NMR, and size exclusion chromatography (SEC) to determine the degree of the substitution (DS), degree of polymerization (DP), and the molecular weight, respectively. Only a minor proportion of PC (ca. 3-15%) was converted to propylene glycol/homooligomers as revealed by high performance liquid chromatography (HPLC). All catalysts promoted preferential derivatization of lignin phenolic OH groups by oxypropyl moieties. The maximum average DP of propylene oxide chains in oxyalkylated Lignoboost (R) kraft lignin (oKL) was 1.85 per one phenylpropane unit (PPU) using DBU. Conversely, the DP of oKL using DICY was very low (0.27/PPU). DICY's catalytic activity seems to be jeopardized due to the formation of unreactive adducts with lignin. The oKL obtained using DBU, DABCO, and K2CO3 have potential to be used as polyols in the production of polyurethanes as the corresponding hydroxyl number (I-OH) is in the range of 198-410 mg KOH g(-1).
publisher WALTER DE GRUYTER GMBH
issn 0018-3830
year published 2020
volume 74
issue 6
beginning page 567
ending page 576
digital object identifier (doi) 10.1515/hf-2019-0274
web of science category Forestry; Materials Science, Paper & Wood
subject category Forestry; Materials Science
unique article identifier WOS:000541917500004
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journal analysis (jcr 2019):
journal impact factor 1.826
5 year journal impact factor 1.828
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