The determination of phenolic hydroxyl groups in coal by thermometric titration

Abstract

The phenolic hydroxyl content of bituminous coals has been determined by grinding the coal with pyridine in a vibratory agate ball mill, adding acetone as a thermometric indicator and titrating with a solution of potassium hydroxide in propan-2-ol.

The results indicate that phenolic hydroxyl accounts for 37 to 62 per cent. of the organic oxygen, depending on the rank of the coal. The individual values obtained are higher than those found for similar coals by potentiometric titration and by acetylation also for high carbon coals. As with these other methods, the greatest proportion of phenolic oxygen was found in coals with about 85 per cent. of carbon on the dry, mineral matter free basis (coal rank code No. 500).

The conclusion is drawn that the higher values obtained by the method described are more correct because the shape of the thermometric titration curves is characteristic of those of sterically hindered phenols, many of which it is known cannot be determined by acetylation or potentiometric titration.