Deuterium as a tracer in coal liquefaction Part 2. Non-catalytic studies

A bituminous Australian coal (Liddell) was liquefied in the absence of catalyst using tetralin as vehicle, and molecular deuterium and hydrogen-deuterium gas mixtures. The structures of the liquid and gaseous products were investigated by mass spectroscopy, ¹H-and ²H-NMR spectroscopy and gel permeation chromatography (GPC). The proportion of ²H to ¹H in the liquid products was found to be higher at 425°C than at 400°C because deuterium preferentially enters more aromatic rings at the higher temperature. The distributions of deuterium in the deuteromethanes formed during liquefaction show that deuterium randomly enters the structural groups in the coal which produce methane before the methane is released to the gas phase. This illustrates the extreme mobility of hydrogen, including the hydrogen that originates from the coal. As a consequence, it is proposed that hydrogen released as methane arises from a pool in which memory of the original bonding is lost.