Hydrogen Production from the LOHC Perhydro-Dibenzyl-Toluene and Purification Using a 5 µm PdAg-Membrane in a Coupled Microstructured System

Abstract

Hydrogen bound in organic liquid hydrogen carriers (LOHC) such as dibenzyl-toluene enables simple and safe handling as well as long-term storage. This idea is particularly interesting in the context of the energy transition, where hydrogen is considered a key energy carrier. The LOHC technology serves as a storage between volatile energy and locally and timely independent consumption. Depending on the type of application, decisive specifications are placed on the hydrogen purity. In the product gas from dehydrogenation, however, concentrations of 100 to a few 1000 ppm can be found from low boiling substances, which partly originate from the production of the LOHC material, but also from the decomposition and evaporation of the LOHC molecules in the course of the enormous volume expansion due to hydrogen release. For the removal of undesired traces in the LOHC material, a pre-treatment and storage under protective gas is necessary. For purification, the use of Pd-based membranes might be useful, which makes these steps less important or even redundant. Heat supply and phase contacting of the liquid LOHC and catalyst is also crucial for the process. Within the contribution, the first results from a coupled microstructured system—consisting of a radial flow reactor unit and membrane separation unit—are shown. In a first step, the 5 µm thick PdAg-membrane was characterized and a high Sieverts exponent of 0.9 was determined, indicating adsorption/desorption driven permeation. It can be demonstrated that hydrogen is first released with high catalyst-related productivity in the reactor system and afterwards separated and purified. Within the framework of limited analytics, we found that by using a Pd-based membrane, a quality of 5.0 (99.999% purity) or higher can be achieved. Furthermore, it was found that after only 8 hours, the membrane can lose up to 30% of its performance when exposed to the slightly contaminated product gas from the dehydrogenation process. However, the separation efficiency can almost completely be restored by the treatment with pure hydrogen.

Viscosity and Surface Tension of Fluorene and Perhydrofluorene Close to 0.1 MPa up to 573 K

“…4 The reverse dehydrogenation can release H 2 upon availability and demand while providing reasonable energy densities. 3,5 Among the hydrocarbon-based LOHC systems, 6−9 the pair diphenylmethane (H0-DPM) and dicyclohexylmethane (H12-DPM) is of practical relevance and suitable for systematic studies due to its lack of regioisomerism, relatively high H 2 storage capacity, 5,8 and comparably low viscosity, 10 facilitating the mass transport of H 2 to and from the catalyst. The hydrogenation and dehydrogenation steps of this system involve next to H0-DPM and H12-DPM also the partially hydrogenated intermediate cyclohexylphenylmethane (H6-DPM).…”

“…Liquid organic hydrogen carriers (LOHCs) have attracted increasing attention as working fluids for the storage and transport of green hydrogen (H 2 ). − By hydrogenation of a hydrogen-lean compound to its hydrogen-rich counterpart, H 2 can be extracted from gas mixtures and stored under ambient conditions in a safe way . The reverse dehydrogenation can release H 2 upon availability and demand while providing reasonable energy densities. , Among the hydrocarbon-based LOHC systems, − the pair diphenylmethane (H0-DPM) and dicyclohexylmethane (H12-DPM) is of practical relevance and suitable for systematic studies due to its lack of regioisomerism, relatively high H 2 storage capacity, , and comparably low viscosity, facilitating the mass transport of H 2 to and from the catalyst. The hydrogenation and dehydrogenation steps of this system involve next to H0-DPM and H12-DPM also the partially hydrogenated intermediate cyclohexylphenylmethane (H6-DPM).…”

Novel Catalysts for Dibenzyltoluene as a Potential Liquid Organic Hydrogen Carrier Use—A Mini-review

“…The membrane is selectively permeable to the products . Wunsch and co-workers demonstrated that microstructure devices and palladium-based membranes are very useful for the production of clean hydrogen. , They developed and investigated a microstructured multistage reactor with a medium separation of hydrogen to observe the perhydro-dibenzyltoluene dehydrogenation process. PdAg membranes were used because of good permeance at a low operating temperature (300–350 °C).…”

Performance Analysis of the Perhydro-Dibenzyl-Toluene Dehydrogenation System—A Simulation Study

“…Various researchers have conducted investigations for the identification of the characteristics of the dehydrogenation reaction conditions. They have reported the following operational conditions for the dehydrogenation system: (1) temperature range of 290-320 • C, (2) pressure below 5 bar [25]. For cycloaliphatic hydrogen carrier molecules, platinum (Pt) is a well-known dehydrogenation catalyst.…”