Studies on the structure of coals: Part 1. The nature of aliphatic groups☆

Abstract

The presence of n-propyl and n-butyl groups in coals was demonstrated by treating coals with sodium hypohalite at 60 °C and measuring the yields of acetic and propionic acids. It was shown that these alkyl groups are fairly stable up to at least 550 °C. A minimum of 3–5% of the total carbon in any coal is shown to exist in n-propyl, while n-butyl accounts for less than 1% of the total carbon in low-rank coals and about 2% in high-rank ones. In low-rank coal at least 17% of the total carbon is present in activated CH2 and/or CH3, and a similar proportion can be activated through nitration of highrank ones. Detection of formic acid in the oxidation products indicates the presence of similarly activated C2H5 groups but a quantitative estimation of such groups could not be given owing to precise analytical difficulties. It is also shown that 550 °C chars are not completely aromatic, at least 14% of the total carbon being non-aromatic (CH2), and 3–4% being contributed by n-propyl and/or n-butyl groups (not the corresponding alkanes).