Effect of dehydrogenation on the structure of two coals

As the quantity and nature of the non‐aromatic material in coals is uncertain, the dehydrogenation of coals has been reinvestigated. Aromatic hydrocarbons, unlike phenolic compounds and compounds containing ‘hydroaromatic’ groups attached to aromatic nuclei, could not be dehydrogenated by sulphur below 200°. It was not possible to predict whether the amount of ‘hydroaromatic’ material in coals might be estimated from their treatment with sulphur. The extent of the dehydrogenation of two coals (rank 902 and 401) with sulphur, and hence the amount of ‘hydroaromatic’ material linked to aromatic nuclei, was estimated from the change in the ratio of the infra‐red absorption at 1430 cm.−1 to that at 1600 cm.−1 Firmer estimates were obtained by dehydrogenating the coals by successive treatment with N‐bromosuccinimide and alcoholic potassium hydroxide. It was concluded that, in agreement with the contentions of the Indian school, 16 ± 2% and 11 ± 2% respectively of the carbon in the coals of rank 902 and 401 was ‘hydroaromatic’ and linked to aromatic nuclei. The manner of the dehydrogenation of the coals by sulphur was considered in some detail and, it being assumed that the above ‘hydroaromaticities’ were correct, it was suggested that the two coals contained few methylene groups which could not be dehydrogenated, and also that the non‐aromatic materials in both coals consisted mainly of ‘hydroaromatic’ methylene groups and methyl substituents.