石炭の炭化初期段階に関する研究 (XVIII)

赤外吸収スペクトル (2)

抄録

Infrared spectra of vitrains of twelve Japanese coals and five foreign coals in different ranks have been measured by the KBr technique as quantitatively as possible. The specific extinction coefficients, K (l/g·cm), at 3, 450, 3, 030 and 2, 920cm^-1 are calculated and their relations with the elementary composition and hydroxyl content are discussed.
The K value at 3, 450cm^-1 assigned to hydroxyl group decreases as the carbon content of coal increases. The relation between hydroxyl content determined by acetylation method and K value shows nearly linear relationship, that is, the K value of this band decreases as the hydroxyl content decreases.
The absorption band at 3, 030cm^-1 which is assigned to aromatic CH hydrogen appears from Bibai coal (81.1%C) and becomes clearer as coal rank increases. The relation between carbon content and K value are found to lie.on the same curve for almost all coals and K value increases with increase in carbon content.
The K value at 2, 920cm^-1 which is assigned to aliphatic CH streching vibration increases gradually as coal rank increases until Yabari coal (86.2%C) except a few coals, but decreases suddenly as coal rank increases above this point. The relation between hydrogen content and K value increases with increase in hydrogen content.
When the ratio of K value of absorption band at 3, 030cm^-1 to that at 2, 920cm^-1 is plotted against carbon content for Japanese coals and foreign coal, almost all coals irrespective of the place of origin are found to lie on the same curve. That is, the ratio of aromatic CH hydrogen to alphatic CH hydrogen increases with increase in coal rank and shows steep increase above 90%C.
Total hydrogen determined by ultimated analysis is subtracted by the hydrogen, in hydroxyl group and this difference is assumed to be CH hydrogen, from which the aromatic and the aliphatic hydrogen is calculated. The ratio of the aromatic hydrogen to the total carbon increases while the ratio of the aliphatic hydrogen to the total carbon decreases, with increasing carbon content.
The aliphatic carbon atoms are assumed to be in CH₂ groups and the difference between the total carbon atoms and the aliphatic carbon atoms is regarded as the aromatic carbon atoms. The ratio of the aromatic carbon to the total carbon increases rapidly with increasing carbon content and reaches 93% for Omine coal (92.2%C).