Elucidation of Hydrogen Mobility of Coal Tar Using a Tritium Tracer Method

Hydrogen Exchange Reaction of Coal Tar with Tritiated Water

Abstract

The hydrogen exchange of coal tar and model compounds of coal tar with water was investigated using a tritium tracer method to elucidate the mobility of hydrogen in coal tar. The reactions at several temperatures in the range from 50 to 300°C were carried out using a batch reactor for 1-12h. The hydrogen exchange ratio (HER) of coal tar with water approached a constant value at 100°C after 6h; however, the HER of coal tar increased remarkably at 200°C and at 300°C with time. From the results obtained from the hydrogen exchange of naphthol and indole as model compounds of coal tar, it was proposed that only hydrogen in functional groups with hetero-atom was exchangeable at 100°C while the hydrogen in the aromatic ring substituted by functional groups with hetero-atom also became exchangeable at 300°C. In contrast to this, the hydrogen in naphthalene hardly exchanged with water even at 300°C. Therefore, it was suggested that the constant value of HER of coal tar at 100°C represented the amount of hydrogen in the coal-tar functional groups with hetero-atom such as hydroxyl group and imino group. It was found that the tritium tracer method was an efficient approach to elucidate the behavior of hydrogen in coal tar and to determine the content of hydrogen related to the functional groups with hetero-atom in coal tar.