H. E. Lerch III R. K. Kotra T.V. Verheyen Patrick G. Hatcher 1988 <p><span>Xylem tissue from degraded wood and coalified logs or stems was examined by pyrolysis g.c.-m.s. to improve understanding of the coalification process. The pyrolysis data, when combined with solid-state&nbsp;</span>¹³<span>C n.m.r. data for the same samples, show several stages of evolution during coalification. The first stage, microbial degradation in peat, involves the selective degradation of cellulosic components and preservation of lignin-like components. As coalification increases, the lignin structural units undergo a series of defunctionalization reactions. The first of these involve loss of methoxyl groups, with replacement by phenolic hydroxyls such that catechol-like structures are produced. As the xylem tissue is converted to subbituminous coal, the persistence of phenols and methylated phenols in pyrolysis g.c.-m.s. data of subbituminous coal suggests that the catechol-like structures are being converted to phenol-like structures. The ability to discern detailed changes in the chemical structural composition of a genetically and histologically related series of samples provides an ideal method for developing models of coal structure, especially that of low-rank coal.</span></p> application/pdf 10.1016/0016-2361(88)90372-9 en Elsevier Pyrolysis g.c.-m.s. of a series of degraded woods and coalified logs that increase in rank from peat to subbituminous coal article