Lignin-phenol-formaldehyde adhesives with residual lignin from hardwood bioethanol production Soo Jung Lee Bioenergy research center at chonnam national university
Contents 1. Background 2. Isolation of lignin from saccharification residues 3. Analysis of isolated lignin 4. Lignin-Phenol-formaldehyde adhesives 5. Conclusion
Background Utilization? Effective utilization of lignocellulosic biomass feedstock Value-added application for low-cost bioethanol production
Characterization of saccharification residue 1728 1370 Utilization of saccharification residues as alternative adhesives to replace phenol? Residue -1) Residu e Raw materia l 2000 1500 1000 2000 1500 1000 Wavenmber (cm - 1 ) prepared nonliquid high proportion of polysaccharide low reactivity impure lignin
Compositional analysis of saccharification residue Yield (%) Chemical composition Holocellulose 37% Organic extractives 11% 50 40 30 Monosaccharide composition 28.4 36.5 acid soluble lignin 0.03% Klason Lignin 46% 20 10 0 0 0.5 5.5 1.2 0.8 Lignin monomer Lignin monomer composition by Nitrobenzene oxidation(nbo) Hydroxy Benzaldehyde Hydroxy benzoic acid Vanillin Vanillic acid Syringaldehyde Syringic acid S/G ratio Yield (%) 0.10 1.52 2.66 2.15 4.50 2.17 1.39
Lignin-Structure CH 2 OH Hydroxylphenyl propane CH 2 OH OH Guaiacyl OCH 3 OH CH 2 OH Lignin of beech wood Nimz, H., 1974. Angew. Chem., 86 (9), 336 344 H 3 CO OH Syringyl OCH 3
Isolation of lignin in saccharification residues Residue after saccharification of hardwood (Quercus acutissima) Treatment with NaOH Treatment with Ethanol-Water H 2 SO 4 /NaOH Residues Filtrate Residues Filtrate 1. Neutralization 2. Concentration 3. Precipitation 1. Remove ethanol by evaporation 2. Acidified Acid insoluble Lignin (AIL) Hemicellulose, Water-soluble Lignincarbohydrate complex Organosolv Lignin (Acid-OSL/Alkali-OSL)
Lignin yield (%)* Yield of isolated lignin 60 40 20 0 * Lignin yield based on klason lignin
Phenolic compound (mg GAE/100g sample) Determination of phenolic compound 30 25 20 15 10 5 0 Analysis of isolated lignin by Folin-Ciocalteau method
Influence of extraction condition Alkali concnetration (%) for alkali-osl 70 0 1 2 3 4 5 6 60 Lignin yield (%) 50 40 30 20 10 0 0 2 4 6 8 10 12 NaOH concentration (%) for AIL 20 30 40 50 60 70 80 Ethanol concentration (%) for OSL
Chemical composition of isolated lignin Yield (%) 14 Vanillin Vanillic acid Syringaldehyde 12 Syringic acid 10 8 6 4 2 0 AIL Acid-OSL Alkali-OSL Lignin monomer composition of isolated lignin using nitrobenzene oxidation by GC * Yield (%) based on lignin sample weight
FTIR-ATR analysis of isolated lignins 0.26 0.24 0.22 0.20 0.18 Alkali-OSL AIL 1460 C-H defoprmantion: aromatic skeletal vibration of benzene ring in lignin Acid-OSL 1505 aromatic skeletal vibration of benzene ring in lignin 1594 C=O stretching conjugated to the aromatic ring 1715 1505 1594 0.16 0.14 AIL 0.12 0.10 0.08 Acid-OSL 0.06 0.04 0.02 Alkali- OSL 0.00 4000 3500 3000 2500 2000 (cm-1) Wavenumbers -1 ) 1500 1000 500
1H-NMR of isolated lignin using acetylation 1 Aliphatic acetate 9 1 2 Acetyl groups in xylan 3 Aromatic acetae 4 H γ, H β, H α in β-o-4 structure 7 Aromatic proton in S- unit 8 Aromatic proton in G-unit 9 Protons in methoxyl groups 8 7 4 2 3 Residues AIL Acid-OSL ppm
Quantitative analysis of isolated lignin Chemical structure of isolated lignins studied by 1 H NMR Sample H G δ H 7.2 6.8 H S δ H 6.8 6.2 OH phen. δ H 2.3 2.1 OH aliph. δ H 2.1 OH ph : OH aliph G:S Residue 0.19 0.29 0.21 0.41 0.52 39:61 AIL 0.21 0.36 0.53 0.73 0.72 37:63 Acid-OSL 0.23 0.38 0.46 0.77 0.6 38:62 Comparison of S/G ratio between methods Comparison of phenolic OH between methods S/G ratio NBO method 1 H-NMR Phenolic OH group UV at 300 nm (%) 1 H-NMR Oak-S-R 1.39 1.55 AIL 2.38 1.7 Acid-OSL 2.39 1.65 Oak-S-R 1.32 0.21 AIL 2.44 0.53 Acid-OSL 2.73 0.46
Bond strength (N/mm 2 ) Performance of adhesives with different lignin Preparation of LPF adhesives 3 2.5 2 Phenol(lignin)/formaldehyde ratio=1:1.5 Mixing : first (phenol+lignin), second (formaldehyde), third (NaOH) Viscosity: 100-300 mpas 1.5 1 0.5 0 Phenol AIL 30% Acid OSL 30% Alkali OSL 30% Residue 30% 110 ± 2 mm 10 ± 0.2 mm
Effect of lignin substitution ratios to phenol
Thermal properties of adhesives Fig. TG curves of PF and LPF obtained from TGA analysis Table. Thermal behavior of LPF compared to PF Adhesives Phenol- Formaldehyde First thermal event T max ( o C) Second thermal event T max ( o C) Third thermal event T max ( o C) Weight residue (%) 208 339 537 69.04 10% Acid-OSL 187 377 492 59.15 30 % Acid-OSL 184 375 484 56.23 40% Acid-OSL 202 370 468 50.68 40% AIL 190 357 488 47.4 40% Alkali OSL 221 301 455 50.90
FTIR-ATR analysis of LPF-adhesives 1230-1260 C-O streching of phenolic OH group 1020 Methylol-OH, aliphatic OH of lignin PF AIL 40% OSL 40% 0 3000 2500 Wav enumbers (cm-1) 2000 1500 1000 2000 1500 1000 Wavenumbers (cm -1 )
Conclusion Isolation of lignin from saccharification necessary because of low reactivity High yield of lignin obtained using alkaline solution or ethanol at room temperature Acid-OSL has higher phenolic OH group and lower S/G ratio compared AIL, supposed more suitable for lignin-phenol-formaldehyde formulation With the increase of the substitution rate of lignin to phenol decreased bonding strength Replacement up to 10% in AIL and acid-osl showed improved adhesive strength 40% of substitution rate in acid-osl decrease only 25% of strength in PF, greater potential to alternative phenol in production of PF-adhesives
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