Hydrogen storage with a naphthenic liquid organic hydrogen carrier (LOHC) obtained from coal tar

Abstract

A method for producing a liquid organic hydrogen carrier (LOHC) from coal tar is proposed. The carrier, a narrow fraction (T10%/T90% = 199/224 °C) with a naphthenic content of ≈99.9 wt%, was obtained through deep hydrogenation of the corresponding fraction of coal tar recovered by vacuum distillation. As a result of hydrogenation, deep purification from sulfur compounds (<5 ppm) was achieved. The composition of the produced carrier was characterized in detail by GCxGC/MS to identify the main components. Further data processing allowed for the calculation of the theoretic hydrogen capacity (6.3 wt %) and hydrogen mass fraction (13.16 wt %). Dehydrogenation in a batch reactor produced a dehydrogenated form of the carrier with a dehydrogenation degree of about ≈82–85%. The main physical properties (density, boiling range, viscosity, and flash/freezing/pour points) were described. The resulting carrier was dehydrogenated in a flow reactor using a Pt/C catalyst, demonstrating stable operation for 108 h. Moreover, the LOHC derived from coal tar exhibited stability in its properties across three consecutive hydrogenation-dehydrogenation cycles conducted over a Pt/C catalyst at 360–370 °C.