Binary Diffusion Coefficients of the Liquid Organic Hydrogen Carrier System Dibenzyltoluene/Perhydrodibenzyltoluene

Abstract

Liquid organic hydrogen carrier (LOHC) systems constitute a very promising concept for future hydrogen storage and logistics. The concept builds on the conversion of excess renewable energy to hydrogen via electrolysis followed by reversible catalytic hydrogenation/dehydrogenation of a diesel-like organic carrier molecule. For an ideal design of the catalytic process, insight into reaction mechanisms and kinetics but also precise knowledge on mass transport properties are necessary. In the present study, binary diffusion coefficients in selected binary LOHC mixtures with five different compositions of perhydrodibenzyltoluene (H 18 -LOHC) and dibenzyltoluene (LOHC) were measured by dynamic light scattering (DLS). The compositions were defined by mixing appropriate amounts of LOHC and H 18 -LOHC to realize different hydrogenation degrees of the LOHC. Binary diffusion coefficients were investigated over a temperature range from (264 to 571) K with an absolute uncertainty of (3 to 25) %. Moreover, an empirical equation describing the binary diffusion coefficients of all five mixture compositions over the complete temperature range with a root-mean-square deviation of less than 3 % was established. It was observed that the binary diffusion coefficient is independent of the hydrogenation degree of LOHC at temperatures above 430 K. For lower temperatures, the binary diffusion coefficient increases with decreasing degree of hydrogenation.

Hydrogen Storage for Mobility: A Review

“…Dibenzyltoluene is another LOHC which is being studied and evaluated [183,184,185,186,187,188]. It can store up to 6.2 wt % at 7.7 MJ/L of hydrogen [189], and it is a liquid substance at ambient temperature with low water solubility, flammability, and toxicity [190].…”

Technologies for the Storage of Hydrogen Part 1: Hydrogen Storage in the Narrower Sense

“…Those are based on oligomers of toluene, usually consisting of two or three toluene units per molecule. The most important example is (di)benzyl toluene . Since the system is a toluene derivative, the reaction temperature is similar to the toluene/methyl hexane system (about 300 C at 1 bar for all homocyclic LOHC systems).…”

Recent Developments in Compact Membrane Reactors with Hydrogen Separation

“…In order to be able to describe the substance system, which has not yet been sufficiently researched for this purpose, firstly, material properties had to be determined [58,59,60,61,62]. Secondly, suitable analytics had to be found to determine the degree of (de)hydrogenation.…”