Speaker
Description
The transition towards a sustainable and carbon-neutral energy future requires the development of innovative technologies that can store and transport energy from intermittent renewable sources such as wind and solar power. Liquid Organic Hydrogen Carriers (LOHC) technology is emerging as a promising solution to address this challenge.
This talk provides an overview of the basics of LOHC technology with a focus on benzyl toluene as a LOHC, covering the catalytic hydrogenation and dehydrogenation processes, reactor types, operating conditions and energy flows.
Benzyltoluene (BT) is readily available and has low toxicity, making it a suitable LOHC candidate. The hydrogen storage capacity is 6.2 %wt or 2.4 MWh/t (HHV). It is a liquid with a high boiling point and low flammability. It has been shown to have good hydrogenation and dehydrogenation kinetics, and the process of hydrogenation and dehydrogenation of benzyltoluene has been extensively studied.
In the LOHC cycle, hydrogen is first added to benzyltoluene to form perhydrogenated benzyltoluene (H12-BT; dicyclohexylmethane) through the exothermic hydrogenation process. The H12-BT molecule is then stored and transported at ambient temperature and pressure, making it a safe and cost-effective alternative to compressed or liquefied hydrogen. When the hydrogen is needed, the H12-BT is endothermically dehydrogenated by exposing it to a suitable catalyst and elevated temperature, resulting in the release of hydrogen gas and the re-formation of benzyltoluene to complete the storage cycle.
The hydrogenation of benzyltoluene (H0-BT) follows the established industrial hydrogenation protocol, using hydrogen pressures of 10 – 50 bar and temperatures of 100 – 300 °C. As catalyst ruthenium and rhodium are used for the lower temperature range, platinum and palladium are used for the higher temperature range.
The energy requirements of the LOHC cycle are an important consideration. The hydrogenation process is exothermic, meaning that energy is released during this step as heat at the temperature level the hydrogenation is run at. For the complete hydrogenation of 1 t of H0-BT to H18-BT an amount of 0.54 MWh of heat is generated. To improve energy efficiency, heat integration can be employed, which involves using heat from the hydrogenation in other processes, e.g. distillative seawater purification.
References
Thermochemical properties of 6,7-benzindole and its perhydrogenated derivative: A model component for liquid organic hydrogen carriers. 2022, Fuel 324. https://dx.doi.org/10.1016/j.fuel.2022.124410
Dehydrogenation of perhydro-N-ethylcarbazole under reduced total pressure. 2021, International Journal of Hydrogen Energy. https://dx.doi.org/10.1016/j.ijhydene.2021.02.128
| Keywords | Hydrogen storage and transport, energy transport, LOHC |
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