Design of a lab-scale plant for the hydrogenation and dehydrogenation of liquid organic hydrogen carriers (LOHC)

The growing demand for low-carbon energy solutions has led to the exploration of alternative energy carriers, including hydrogen. Renewable hydrogen (i.e. hydrogen generated from electrolysis through renewable energy sources) is expected to play a relevant role in the energy transition of hard-to-abate sectors like heavy-duty transport and industrial high-temperature processes. However, hydrogen poses significant technical, economic, and safety challenges related to its storage and transportation. Liquid Organic Hydrogen Carriers (LOHCs) are emerging as a promising technology to address these barriers, offering a safe and efficient alternative to gaseous or liquid hydrogen storage. The paper focuses on the design of a laboratory-scale plant for the hydrogenation and dehydrogenation of LOHCs, with the future goal of optimising operating conditions and maximising process efficiency for hydrogen seasonal storage. After an overview of the various hydrogen storage technologies, the role of LOHCs is examined in detail, with particular attention to compounds such as dibenzyltoluene, benzyltoluene, and toluene. These compounds allow for hydrogen storage and its release through catalysed reactions. The laboratory plant design features a flexible configuration that can operate in both hydrogenation and dehydrogenation modes, utilising a vertical reactor equipped with platinum-on-alumina (Pt/Al₂O₃) catalysts, which are chosen for their effectiveness in both stages of the process. Particular attention was paid to analysing optimal operating conditions to improve the degree of hydrogenation (DoH) and the degree of dehydrogenation (DoD). Various methodologies, including measurements of density, viscosity, and refractive index, can be used to evaluate DoH and DoD, i.e., the efficiency of the process. Finally, the paper describes the design process of the reactor and illustrates the executive piping and instrumentation diagram (P&ID) of the lab-scale plant, along with its main components.