Influence of catalyst bed configurations on the thermal behavior of an Ohmic reactor for LOHC dehydrogenation

Within the Liquid Organic Hydrogen Carrier (LOHC) concept, where the dehydrogenation of perhydro-benzyltoluene is a highly endothermic process, efficient thermal management is crucial to maintain reaction performance. Ohmic heating offers a promising solution by enabling direct volumetric heat generation within the catalyst bed, thereby overcoming the limitations associated with conventional external heating. This thesis investigates the thermal behavior of an ohmic packed-bed reactor containing alternating layers of activated carbon (AC) pellets and graphite fleece (GF), which serve as conductive catalyst supports.
Ten bed configurations were experimentally evaluated under varying insulation, preheating, and flow conditions to determine their effect on axial temperature uniformity. The results revealed that the reactor’s temperature distribution is governed by the combined influence of bed architecture, resistive material arrangement, and external heat losses. Although the axial arrangement of AC and GF layers primarily determined the temperature uniformity in all cases, in uninsulated beds continuous heat losses through walls and electrodes also contributed to the profile in certain configurations. Configurations with thicker AC sections at both ends achieved balanced heat generation and smoother thermal gradients under insulated conditions.
Complementary COMSOL Multiphysics simulations supported the experimental findings, providing quantitative insight into temperature distribution within different bed configurations. The developed model represents the real system well and provides a reliable basis for analyzing temperature distributions across different configurations. Ultimately, this work provides a systematic foundation for integrating ohmic heating into catalytic packed-bed systems, advancing the development of energy efficient, distributed heating technologies for sustainable hydrogen storage and release.