Impurities in hydrogen released from perhydro benzyltoluene - Assessment and adsorptive removal

Liquid Organic Hydrogen Carriers (LOHC) technologies offer viable options to overcome most issues linked to the storage of elemental hydrogen. They involve the chemical binding of hydrogen to carrier molecules through reversible catalytic hydrogenation/dehydrogenation cycles. Hydrogen, released from LOHC systems should thereby meet high purity requirements. In this contribution, the quality of hydrogen released from the LOHC compound perhydro benzyltoluene (H12-BT) is assessed and a suitable adsorptive purification process is described. Our study considers volatile and semi-volatile organic compounds (VOCs and SVOCs), methane, CO, CO₂, and water impurities found in the product stream of a continuous dehydrogenation rig operating at power levels between 1.4 and 4.3 kW_H2-LHV. We determine the influence of dehydrogenation process parameters (e.g., temperature, pressure, LOHC flow rate, LOHC quality) on the hydrogen quality and demonstrate that a combination of silica- and carbon-based adsorbents is highly suitable for removing VOCs and SVOCs from the hydrogen product stream. Using optimized process and purification conditions the released hydrogen fulfills the requirements defined by ISO 14687 for fuel cell applications.