Selected genera represented by recent and peatified woods common to the southeastern US and their lignitic equivalents from Vermont and North Dakota have been characterized by Curie-point pyrolysis-mass spectrometry and Curie-point pyrolysis-gas chromatography, mass spectrometry. Pyrolysis data have shown that similar chemical trends are exhibited during the peatification and early coalification of both hardwood and softwood cell wall components. These trends are:

  1. (1) the relatively rapid removal of pentosans i.e., hemicelluloses),
  2. (2) the initial enrichment followed by the gradual removal of cellulose (and other hexose sugars), and
  3. (3) the gradual modification of lignin to a less functionalized aromatic polymer. These observations imply that cell wall-derived huminitic macerals in coals consist predominantly of demethoxylated, demethylated, and more highly condensed lignin derived macromolecules.
Geochim. Cosmochim. Acta

Stout, S. A., Boon, J. J., & Spackman, W. (1988). Molecular aspects of the peatification and early coalification of angiosperm woods. Geochim. Cosmochim. Acta, 52, 405–414. doi:10.1016/0016-7037(88)90096-8