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).
keywords
RING-OPENING POLYMERIZATION; PROPYLENE CARBONATE; CYCLIC CARBONATES; OXYPROPYLATION; POLYOLS; XYLAN
subject category
Forestry; Materials Science
authors
Vieira, FR; Barros-Timmons, A; Evtuguin, DV; Pinto, PCR
our authors
Ana Margarida Madeira Viegas de Barros Timmons
Associate Professor
Dmitry Evtyugin
Associate Professor with Aggregation
Fernanda Vieira
Collaboratoracknowledgements
This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the Portuguese Foundation for Science and Technology/MCTES and the Project Inpactus - innovative products and technologies from eucalyptus, project no. 21874 funded by Portugal 2020 through European Regional Development Fund (ERDF) within the frame of COMPETE 2020 n degrees 246/AXIS II/2017.