Direct Thermochemical Liquefaction

Lignin

Lignin

Lignin is the second most abundant biomass component and the only renewable aromatic resource in nature. Lignin pyrolysis has been studied for almost 100 years with the focus on two different aspects:

  • Unravelling the structure of the aromatic biopolymer;
  • Production of monomeric phenols.

Good overviews on both pathways, covering the years 1920-1980, are given by Goldstein [1] and Allan and Mattila [2]. During the past 25 years little attention has been paid to the use of lignin as a chemical resource. This time period was reviewed by Amen-Chen et al. [3].

Fast pyrolysis of lignin has been used for studying degradation mechanisms by advanced analytical pyrolysis methods (Curie point pyrolysis, heated filament, micro-oven) combined with hyphenated separation and detection systems (GC/MS) [4-7]. Mass spectral information was provided by Faix et al. [8]. Influence of pyrolysis conditions on the kinetics of lignin pyrolysis was recently investigated by Britt et al. [9].

With the upcoming focus on biorefineries, lignin has gained new interest as a resource for renewable aromatic chemicals, as the supply of fossil feedstocks is becoming more and more insecure and expensive. Apart from biorefineries, kraft lignin will soon be available in large amounts, as advanced precipitation technologies have been developed recently [10-12].

The simple pyrolysis of lignin (both fast or slow) suffers from three principle problems:

  • Feeding is difficult, as lignin tends to melt around 90°C;
  • Low yields of monomeric aromatics (5-15 wt%);
  • Wide spectrum of alkylated aromatics, which are less prone to further reactions.

These observations became obvious in a recent round robin testing organized by the IEA Task 34 [13].

To increase yields and to simplify the composition of the monomeric products, advanced processes are needed such as hydrocracking. In the presence of a suitable catalyst and under hydrogen pressure better yields and more attractive compositions can be expected [14-19].

References

[1] Goheen, D.W., Chemicals from lignin, CRC, 1981, pp. 143-161.
[2] Allan, G.G. and Mattila, T., High energy degradation, in lignins – Occurrence, Formation Structure and Reactions, K.V. Sarkanen, C.H. Ludwig, (Eds.), Wiley Interscience, New York, London, Sydney, 1971, pp. 575-596.
[3] Amen-Chen, C., Pakdel, H. and Roy, C., Production of monomeric phenols by thermochemical conversion of biomass: a review, Bioresource Technology, 79, 277-299 (2001).
[4] Lopes, F.F., Silverio, F.O., Baffa, D.C.F., Loureiro, M.E. and Barbosa, M.H.P., Determination of Sugarcane Bagasse Lignin S/G/H Ratio by Pyrolysis GC/MS, J. Wood Chemistry and Technology, 31, 309-323 (2011).
[5] Laskar, D.D., Ke, J., Zeng, J., Gao, X. and Chen, S., Py-GC/MS as a powerful and rapid tool for determining lignin compositional and structural changes in biological processes, Current Analytical Chemistry, 9, 335-351 (2013).
[6] Vinciguerra, V., Spina, S., Luna, M., Petrucci, G. and Romagnoli, M., Structural analysis of lignin in chestnut wood by pyrolysis-gas chromatography/mass spectrometry, Journal of Analytical and Applied Pyrolysis, 92, 273-279 (2011).
[7] del, R.J.C., Rencoret, J., Prinsen, P., Martinez, A.T., Ralph, J. and Gutierrez, A., Structural Characterization of Wheat Straw Lignin as Revealed by Analytical Pyrolysis, 2D-NMR, and Reductive Cleavage Methods, Journal of Agricultural and Food Chemistry, 60, 5922-5935 (2012).
[8] Faix, O., Meier, D. and Fortmann, I., Thermal degradation products of wood. A collection of electron-impact (EI) mass spectra of monomeric lignin derived products, Holz als Roh- und Werkstoff, 48, 351-354 (1990).
[9] Britt, P.F., Buchanan, A.C. and Kidder, M.K., Pyrolysis mechanisms of lignin model compounds, American Chemical Society, 2008, pp. Fuel-137.
[10] Jankovic, B., The comparative kinetic analysis of Acetocell and Lignoboost® lignin pyrolysis: the estimation of the distributed reactivity models, Bioresource Technology, 102, 9763-9771 (2011).
[11] Beis, S.H., Mukkamala, S., Hill, N., Joseph, J., Baker, C., Jensen, B., Stemmler, E.A., Wheeler, M.C., Frederick, B.G., van, H.A., Berg, A.G. and De, S.W.J., Fast pyrolysis of lignins, BioResources, 5, 1408-1424 (2010).
[12] Tomani, P., The Lignoboost process, Cellulose Chemistry and Technology, 44, 53-58 (2010).
[13] Nowakowski, D.J., Bridgwater, A.V., Elliott, D.C., Meier, D. and de Wild, P., Lignin fast pyrolysis: Results from an international collaboration, Journal of Analytical and Applied Pyrolysis, 88, 53-72 (2010).
[14] Li, C., Zheng, M., Wang, A. and Zhang, T., One-pot catalytic hydrocracking of raw woody biomass into chemicals over supported carbide catalysts: simultaneous conversion of cellulose, hemicellulose and lignin, Energy and Environmental Science., 5, 6383-6390 (2012).
[15] Marker, T.L. and Petri, J.A., Production of gasoline, diesel. naphthenes and aromatics from lignin and cellulose waste one step hydrocracking, Aug. 9, 2011, UOP LLC, Des Plaines, IL, USA, 2011.
[16] Meier, D., Catalytic hydrocracking of lignins to useful aromatic feedstocks, DGMK Tagungsber., 2008-3, 299-304 (2008).
[17] Johnson, D.K., Chum, H.L., Anzick, R. and Baldwin, R.M., Preparation of a lignin-derived pasting oil, Applied Biochemistry and Biotechnology, 24-25, 31-40 (1990).
[18] Koyama, M., Kanazawa, K., Yamadaya, M., Sugimoto, G. and Nakasato, S., Hydrocracking of Lignin I. Effects of reaction temperature and iron catalysts, Mokuzai Gakkaishi, 33, 571-575 (1987).
[19] Parkhurst, H.J., Huibers, D.T.A. and Jones, M.W., Production of phenol from lignin, ACS Symp. Ser. Altern. (Feedst. Petrochem. Div. Petroleum Chem.), 25, 24-29 (1980).