Polymers in coals, lignin-like

Structural Characterization of Coal Lignin-Like Polymers in Coals... 

Alkaline cupric oxidation of coals produced phenolic acids (p-hydroxy and 3,4 hydroxy-benzoic acids, 4 hydroxy l,2 and 4-hydroxy l,3 benzenedicarboxylic acids), which are known as characteristic lignin oxidation products. The results indicate that lignin-like polymers are incorporated into macromolecules of coals and still are identifiable in lower rank coals. 

Although one cannot rule out the possibility that plant phenols (3, 22, 35) could be one of the important precursors for coal formation, the present work shows that lignin-like polymers have been incorporated into the macromolecules of coals, and are still identifiable in lower-rank coals. Evidence for this is the identification of p-hydroxy- and 3,4-dihydroxy-benzoic acids, and hydroxybenzenedicarboxylic acids which are known lignin oxidation products. 

In a previous paper (21) we characterized aromatic acids trapped in lignite coal, and have found that these acids are quite similar qualitatively to those obtained from the present oxidation of the same pretreated coal. This indicated that the trapped acids were derived mainly from the hydrolytic degradation of lignin-like polymers. We also have observed that no trapped organic acid is isolated from the anthracite coal that no longer contains lignin-like polymers. 

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