Title: Understanding the chemical transformations of lignin during ionic liquid pretreatment
DOI: 10.1039/c3gc41752b
Abstract: Unveiling the fundamental chemistry of lignin under ionic liquid (IL) pretreatment will facilitate the understanding of biomass recalcitrance involved in pretreatment processes. To examine in greater detail the chemical transformations of lignin under difffferent IL pretreatment conditions without competing reactions from plant polysaccharides, the IL pretreatment of the isolated poplar alkaline lignin (hardwood lignin) under varying IL pretreatment conditions (i.e., 110–170 °C,1–16 hours) was performed in an appropriate manner. The structural transformations of the lignin have been investigated by elemental analysis, 2D-HSQC spectra, quantitative 13C-NMR spectra, 31P NMR, and GPC analysis. Results revealed that a decrease of aliphatic OH and an increase in phenolic hydroxyl groups occurred in lignin as the pretreatment proceeded. The increased phenolic OH was mainly as a result of cleavage of β-O-4’ linkages, while the reduced aliphatic, OH is probably attributed to the dehydration reaction. The cleavage of β-O-4’ linkages, degradation of β–β’ and β-5’ linkages obviously happened at high temperatures and resulted in the decrease of molecular weights. In addition, IL pretreatment selectively degraded the G-type lignin fractions and the condensation reaction took place more easily at S units than G units. Moreover, the demethoxylation preferentially occurred in G units, especially at higher temperatures. It is believed that investigating the fundamental chemistry of lignin during IL pretreatments would be benefificial to optimize and control the pretreatment process.
Experiment process:
Four characterization analysis:
Result discussion:
Reference:
1 A. K. Sangha, L. Petridis, J. C. Smith, A. Ziebell and J. M. Parks, Environ. Prog. Sustain., 2012, 31, 47–54.
2 M. E. Himmel, S. Y. Ding, D. K. Johnson, W. S. Adney, M. R. Nimlos, J. W. Brady and T. D. Foust, Science, 2007, 315, 804–807.
3 T. Q. Yuan, F. Xu and R. C. Sun, J. Chem. Technol. Biotechnol., 2013, 88, 346–352.
4 S. Nakagame, R. P. Chandra, J. F. Kadla and J. N. Saddler, Biotechnol. Bioeng., 2011, 108, 538–548.
5 M. H. Studer, J. D. DeMartini, M. F. Davis, R. W. Sykes, B. Davison, M. Keller, G. A. Tuskan and C. E. Wyman, Proc. Natl. Acad. Sci. U. S. A., 2011, 108, 6300–6305.
6 X. J. Pan, D. Xie, N. Gilkes, D. J. Gregg and J. N. Saddler, Appl. Biochem. Biotechnol., 2005, 121, 1069–1079.
7 (a) X. B. Zhao, L. H. Zhang and D. H. Liu, Biofuel. Bioprod. Bior., 2012, 6, 465–482; (b) X. B. Zhao, L. H. Zhang and D. H. Liu, Biofuel. Bioprod. Bior., 2012, 6, 561–579.
8 T. Welton, Green Chem., 2011, 13, 225–225.
9 A. Brandt, J. Gräsvik, J. P. Hallett and T. Welton, Green Chem., 2013, 15, 550–583.
10 P. Mäki-Arvela, I. Anugwom, P. Virtanen, R. Sjöholm and J. P. Mikkola, Ind. Crop. Prod., 2010, 32, 175–201.
11 N. Sun, M. Rahman, Y. Qin, M. L. Maxim, H. Rodríguez and R. D. Rogers, Green Chem., 2009, 11, 646–655.
12 J. Y. Kim, E. J. Shin, I. Y. Eom, K. Won, Y. H. Kim, D. Choi, I. G. Choi and J. W. Choi, Bioresour. Technol., 2011, 102, 9020–9025.
13 J. L. Wen, S. L. Sun, B. L. Xue and R. C. Sun, J. Agric. Food Chem., 2013, 61, 635–645.
14 Ö. P. Çetinkol, D. C. Dibble, G. Cheng, M. S. Kent, B. Knierim, M. Auer, D. E. Wemmer, J. G. Pelton, Y. B. Melnichenko and J. Ralph, Biofuels, 2010, 1, 33–46.
15 K. M. Torr, K. T. Love, Ö. P. Çetinkol, L. A. Donaldson, A. George, B. M. Holmes and B. A. Simmons, Green Chem., 2012, 14, 778–787.
16 P. Varanasi, P. Singh, R. Arora, P. D. Adams, M. Auer, B. A. Simmons and S. Singh, Bioresour. Technol., 2012, 126, 156–161.
17 G. Cheng, P. Varanasi, C. Li, H. Liu, Y. B. Melnichenko, B. A. Simmons, M. S. Kent and S. Singh, Biomacromolecules, 2011, 12, 933–941.
18 S. H. Lee, T. V. Doherty, R. J. Linhardt and J. S. Dordick, Biotechnol. Bioeng., 2009, 102, 1368–1376.
19 C. Li, L. Sun, B. A. Simmons and S. Singh, BioEnerg. Res., 2013, 6, 14–23.
20 P. Whiting and D. Goring, Wood Sci. Technol., 1982, 16, 261–267.
21 A. Ziebell, K. Gracom, R. Katahira, F. Chen, Y. Q. Pu, A. J. Ragauskas, R. A. Dixon and M. Davis, J. Biol. Chem., 2010, 285, 38961–38968.
22 J. Ralph, T. Akiyama, H. D. Coleman and S. D. Mansfield, BioEnergy Res., 2012, 5, 1009–1019.
23 W. Y. Li, N. Sun, B. Stoner, X. Jiang, X. Lu and R. D. Rogers, Green Chem., 2011, 13, 2038–2047.
24 J. A. Perez-Pimienta, M. G. Lopez-Ortega, P. Varanasi, V. Stavila, G. Cheng, S. Singh and B. A. Simmons, Bioresour. Technol., 2013, 127, 18–24.
25 T. Q. Yuan, S. N. Sun, F. Xu and R. C. Sun, J. Agric. Food Chem., 2011, 59, 6605–6615.
26 R. C. Sun, J. M. Fang and J. Tomkinson, J. Wood Chem. Technol., 1999, 19, 335–356.
27 A. Sluiter, B. Hames, R. Ruiz, C. Scarlata, J. Sluiter, D. Templeton and D. Crocker, Laboratory analytical procedure (LAP): Determination of structural carbohydrates and lignin in biomass, Technical Report: NREL/TP-510-42618, National Renewable Energy Laboratory, Golden, CO, USA, 2008.
28 M. Sette, R. Wechselberger and C. Crestini, Chem.–Eur. J., 2011, 17, 9529–9535.
29 T. Q. Yuan, S. N. Sun, F. Xu and R. C. Sun, J. Agric. Food Chem., 2011, 59, 10604–10614.
30 J. C. Del Rio, J. Rencoret, G. Marques, J. B. Li, G. Gellerstedt, J. Jiménez-Barbero, Á. T. Martínez and A. Gutiérrez, J. Agric. Food Chem., 2009, 57, 10271–10281.
31 J. L. Wen, S. L. Sun, B. L. Xue and R. C. Sun, Materials, 2013, 6, 359–391.
32 J. Ralph and L. L. Landucci, NMR of lignins, CRC Press, 2010, pp. 137–244.
33 B. B. Hallac, Y. Pu and A. J. Ragauskas, Energy Fuels, 2010, 24, 2723–2732.
34 Y. Pu, S. Cao and A. J. Ragauskas, Energy Environ. Sci., 2011, 4, 3154–3166.
35 C. Crestini and D. S. Argyropoulos, J. Agric. Food Chem., 1997, 45, 1212–1219.
36 Y. Pu, F. Hu, F. Huang, B. H. Davison and A. J. Ragauskas, Biotechnol. Biofuels, 2013, 6, 1–13.
37 G. Cheng, M. S. Kent, L. He, P. Varanasi, D. Dibble, R. Arora, K. Deng, K. Hong, Y. B. Melnichenko, B. A. Simmons and S. Singh, Langmuir, 2012, 28, 11850– 11857.
38 A. George, K. Tran, T. J. Morgan, P. I. Benke, C. Berrueco, E. Lorente, B. C. Wu, J. D. Keasling, B. A. Simmons and B. M. Holmes, Green Chem., 2011, 13, 3375–3385.
39 W. Ji, Z. Ding, J. Liu, Q. Song, X. Xia, H. Gao, H. Wang and W. Gu, Energy Fuels, 2012, 26, 6393–6640.
From:Zhou Min