Hardwood, lignin pyrolysis

Pyrolysis has a long history in the upgrading of biomass. The dry distillation of hardwood was applied in the early 1990s to produce organic intermediates (methanol and acetic acid), charcoal and fuel gas [3]. Today s processes can be tuned to form char, oil and/or gas, all depending on the temperature and reaction time, from 300 °C and hours, to 400-500 °C and seconds-minutes, to >700 °C and a fraction of a second [3, 19, 23, 24], The process is typically carried out under inert atmosphere. We illustrate the basic chemistry of pyrolysis by focusing on the conversion of the carbohydrate components (Fig. 2.4). The reaction of the lignin will not be covered here but should obviously be considered in a real process. Interested readers could consult the literature, e.g., [25]. Pyrolysis is discussed in more details elsewhere in this book [26],... 

Muller M (1980) Beitrag zum Einsatz der Curie Punkt-Pyrolyse Massenspektrometrie in der Analytik von Naturstoffen Dissertation ETH 6743, Zurich Obst JR (1983) Analytical pyrolysis of hardwood and softwood lignins and its use in lignin type determination of hardwood vessel elements J Wood Sci Technol 3 377-397 Pouwels AD, Boon JJ (1987) Analysis of lignin and chlorohgntn residues in a beech xylan fraction by pyrolysis gas chromatography mass spectrometry J Wood Sci Technol 7 197— 213... 

The pyrolysis oil collected between 200 to 275 C in the second step was 18.14 % by wt. on an anhydrous wood basis and corresponded to the hemicelluloses degradation . In general, hemicelluloses decompose to yield furans and its derivatives as well as a series of aliphatic carboxylic acids. Hardwoods are composed of pentosan-based hemicelluloses, while hexosan-based hemicelluloses are found in softwoods. Hardwood produces more low molecular weight carboxylic acids and furans than softwood upon decomposition . In contrast, hardwood contains a lower quantity of fatty acids than softwood. Cl - C6 carboxylic acids, fatty acids (e.g. Cia), fiiran and derivatives were identified in this fraction. In the second pyrolysis step, a little rearrangement of the lignin polymer occurred which was based on the formation of small amount of phenolic compounds 0,395 % by wt., anhydrous wood basis). The main components of this fraction are listed in Table 2. Betulin and lupeol were abundant in this fraction. Furthermore, levoglucosan which has been reported earlier as a major compound in the cellulose-derived pyrolysis oils, was identified in the second... 

Techniques such as Py-MS or Py-GC/MS are not always suitable for the identification of less volatile or highly polar compounds. HPLC analysis with MS detection provides a better tool in such cases, and it was successfully applied for lignin pyrolysate analysis (see Section 5.7). Pyrolysis products from a lignin sample from mixed hardwood, obtained using the organosolv procedure with ethanol/water and generated at 510° C in an on-line Curie point pyrolyser and analyzed by HPLC [8], indicated the presence of a series of compounds shown in Table 9.1.7. 

Table 9.1.7. Pyrolysis products from lignin from mixed hardwood generated at 51(f C in an on-line Curie point pyrolyser and analyzed by HPLC.

Pyrolysis-GC with MS detection in the SIM mode was applied to the characterization of natural and industrial lignins of various species, as for the presence of p-hydroxyphenyl (65a), guaiacyl (65b) and syringyl (65c) moieties. This objective was achieved after permethylation of the lignin samples. Such moieties are characteristic of ligin in straw, softwoods and hardwoods, respectively. ... 

TG/DTG together with IR analysis was applied for the isothermal pyrolysis of Klason lignins from some Argentinian hardwoods in the temperature region... 

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