(170e) Energy and Carbon Foot Print Analysis of the Production of a Liquid Organic Hydrogen Carrier

In a future energy system based on renewable energies, energy carriers and storage systems are required to store excess energy for times with low provision of energy from renewable resources. In this context, hydrogen is considered as a suitable energy carrier although the efficient, dense and secure storage of hydrogen is still a challenge.

A promising approach to overcome this limitation is the use of liquid organic hydrogen carriers (LOHCs). LOHCs are unsaturated organic compounds which can store hydrogen by reversible hydrogenation (e.g. dibenzyltoluene). The hydrogenated form of the LOHC exhibits high thermodynamic stability, enabling storage at ambient conditions. In contrast to the application of solid chemical carrier substances e.g. metal hydrides, the handling and transportation of the LOHC rather easy due to the liquid nature of the carrier substance.

A lot of research was performed concerning the LOHC storage concept in terms of applicability and efficiency but only little is known about the energy demand and the ecological impact of the production of the carrier as such. Especially the carbon foot print of an energy carrier substance is important to ensure the overall ecological benefit of the storage concept.

In this contribution, we present a process concept for the production of the LOHC dibenzyltoluene on technical scale. Based on the process concept, the heat and electricity demand is determined and potential energy savings are identified by a pinch analysis. Moreover, a carbon foot print analysis is performed to reveal the ecological impact related to the production of the LOHC.

First results show that the main energy demand of the overall process is linked to the product purification steps. Especially for low conversions in the synthesis reactor this energy demand increases remarkably. By rigorous heat coupling of the overall process, the overall heat demand can be lowered by about 35 %.