12. February 2016
How fundamental EAM research turns into real business – Transport and storage of hydrogen via Liquid Organic Hydrogen Carrier (LOHC) systems
Since 2011, EAM has supported research on hydrogen storage and transport using Liquid Organic Hydrogen Carrier (LOHC) systems. LOHC systems consist of pairs of at least one hydrogen-lean, typically aromatic or heteroaromatic liquid and at least one hydrogen-rich, saturated alicyclic or heteroalicyclic liquid. During hydrogen storage, the hydrogen-lean compound is converted in a catalytic hydrogenation reaction under hydrogen pressure into the corresponding hydrogen rich compound. The latter can be stored and transported in the existing infrastructure for liquid fuels. At the time and place of energy demand or need for hydrogen, the hydrogen-rich compound is brought in contact with a dehydrogenation catalyst to release the stored hydrogen. The carrier can be charged and discharged many times like a “deposit bottle” for hydrogen. Requirements for a suitable LOHC system are high hydrogen capacity (typically 5.0 to 7.2 mass% hydrogen or 1.5 to 2.4 kWhtherm/kg), very selective hydrogenation and dehydrogenation reactions under suitable pressure and temperature conditions, large liquid range, low cost, easy handling and benign ecotoxicology. It was the car manufacturer BMW who initially brought up the topic of LOHC to researchers of EAM Research Area D Catalytic Materials. It was developed within a strategic EAM collaboration involving researchers from physical chemistry (Prof. H.-P. Steinrück, Prof. J. Libuda), reaction engineering (Prof. P. Wasserscheid, Prof. W. Schwieger), separation science (Prof. W. Arlt), fluid mechanics (Prof. A. Delgado) and material science (Prof. R. F. Singer, Prof. C. Körner). The fundamental EAM research formed the basis for more applied projects funded by the Bavarian Hydrogen Center and by the Energie Campus Nürnberg with more FAU researchers joining in (Prof. E. Schlücker, Process Technology and Machinery, Prof. M. Wensing, Prof. S. Will, Engineering Thermodynamics).
The topic developed into a widely visible Erlangen effort in energy technologies that also helped to establish the new Helmholtz-Institute HI ERN. Moreover, research and development on stationary, LOHC-based energy storage systems paved the way for the FAU spin-off company, Hydrogenious Technologies GmbH founded in January 2013. Today, the company has 20 employees and acts as manufacturer and full-service provider of LOHC-based hydrogen storage and transportation systems. Hydrogenious Technologies’ head office, laboratories and production facilities are located in Erlangen-Bruck. The company’s investor, Anglo American Platinum, is the world’s biggest producer of platinum and precious group metals. Anglo is convinced that LOHC technology offers great potential to facilitate a much broader utilization of hydrogen-based energy systems. Such a breakthrough would push market demand for Pt group metals to equip LOHC conversion systems along with electrolyzers and fuel cells.
Among the LOHC systems tested and evaluated over the last five years of research, the system dibenzyltoluene/perhydrodibenzyltoluene is the most promising. Dibenzyltoluene has been used for many decades in large quantities as an industrial heat transfer fluid, has already been well investigated and found to be very suitable for its use as hydrogen carrier: the material is non-toxic, non-carcinogenic and non-mutagenic. The material is liquid down to -30 °C and its boiling point is above 360 °C. Moreover, due to its industrial availability the material is inexpensive: On a larger scale (> 1000 kg) a kilogram of dibenzyltoluene costs below 5 €. The joint invention of this new LOHC system by EAM and BMW researchers in 2012 is regarded today as a breakthrough towards an industrial application of the technology. First containerized plants have been sold by Hydrogenious Technologies in 2015. An impression of such energy storage containers is given in Figure 1.
Apart from the promise of commercial success of the LOHC technology there remain many fundamental scientific questions that will keep EAM researchers busy over the next years: How to make the hydrogenation/dehydrogenation catalysis even more efficient in terms of space-time-yield and precious metal utilization? How to further optimize heat integration and hydrogen/LOHC separation? How to combine LOHC hydrogenation/dehydrogenation catalysis with electrolyzer/fuel cell functionalities in direct energy conversion units? These and related scientific questions are ideally suited for a multi-disciplinary research environment specializing in materials and processes, such as EAM.
No matter whether we look at catalytic processes in chemical industry, at environmental catalysis or at new devices for energy storage and transformation, metallic nanoparticles are omnipresent in new and emerging technologies. Their special chemical and physical properties are at the heart of modern methods and devices that help to make more efficient use of our materials and energy resources. Often the special properties of nanoparticles are not intrinsic but they arise from a chemical interaction with their surroundings, for example with the support material that they are placed on. Such interactions often change the electronic structure of the nanoparticle, for instance because electrical charge is exchanged between the particle and the support. Reporting in Nature Materials, the research groups of Prof. J. Libuda (EAM/FAU) and Prof. K. Neyman (Barcelona) and their cooperation partners reveal how the number of elementary charges lost by a platinum nanoparticle when it is placed onto an oxide support can be counted. The magnitude of the effect is surprisingly large: Approximately every tenth metal atom loses an electron when the particle comes in contact with the oxide.
To measure the electrical charge exchanged between the catalyst particle and its surrounding the international team of researchers from Germany, Spain, Italy and the Czech Republic prepared an extremely clean and atomically well-defined oxide surface, on which they placed platinum nanoparticles. Using a highly sensitive detection method at the Synchrotron Radiation Source Elettra in Trieste the researchers could, for the first time, count the number of transferred electrons for particles having up to hundreds of atoms. Using theoretical methods they could rationalize the effects and show how the charge transfer can be tuned to adjust the chemical properties. The latter would help to optimize a catalytic process and make more efficient use of materials and energy resources.
Selected EAM publications dealing with hydrogen storage using the LOHC technology:
Evaluation of Industrially Applied Heat-Transfer Fluids as Liquid Organic Hydrogen Carrier Systems
Nicole Brückner, Katharina Obesser, Andreas Bösmann, Daniel Teichmann, Wolfgang Arlt, Jennifer Dungs, Peter Wasserscheid
ChemSusChem, 2014, 7, 229-235
Surface Science Studies of Carbazole Derivatives
Christian Papp, Peter Wasserscheid, Jörg Libuda, Hans-Peter Steinrück
The Chemical Record, 2014, 14, 879-896
Efficient Hydrogen Release from Perhydro-N-ethylcarbazole Using Catalyst-Coated Metallic Structures Produced by Selective Electron Beam Melting
Willi Peters, Martin Eypasch, Torsten Frank, Jan Schwerdtfeger, Carolin Körner, Andreas Bösmann, Peter Wasserscheid
Energy & Environmental Science, 2015, 8, 641-649
Macrokinetic effects in perhydro-N-ethylcarbazole dehydrogenation and H2 productivity optimization by using egg-shell catalysts
Willi Peters, Alexander Seidel, Stefan Herzog, Andreas Bösmann, Wilhelm Schwieger, Peter Wasserscheid
Energy & Environmental Science, 2015, 8, 3013–3021