Experimental assessment of the degree of hydrogen loading for the dibenzyl toluene based LOHC system

Liquid Organic Hydrogen Carriers allow for storing hydrogen with high density at ambient conditions. In the LOHC hydrogen storage process, a significant number of different partially and fully hydrogenated species occur on the reaction pathway from the hydrogen-lean to the hydrogen-rich form of the LOHC system. In order to access the amount of hydrogen stored in the carrier system, ways of measuring the degree of hydrogenation are required. A number of physical properties can be correlated with the degree of hydrogenation. However, there are different mixtures of hydrogenated, partly hydrogenated and dehydrogenated derivatives which result in an identical degree of hydrogenation but different properties. In this contribution we report on attempts to correlate physico-chemical properties and spectroscopic data to the degree of hydrogenation of the dibenzyl toluene system by using density, viscosity, refractive index, UV-VIS and Raman spectroscopy measurements. The most reliable correlations were found for density or refractive index.