Heat transfer to a catalytic multiphase dehydrogenation reactor
Miriam Willer, Patrick Preuster, Paolo Malgaretti, Jens Harting, Peter Wasserscheid
Abstract
The release of hydrogen from liquid organic hydrogen carriers (LOHC) takes place in an endothermal dehydrogenation reaction that is accompanied by a strong volume expansion. This leads to complex hydrodynamic properties that change drastically along the reactor axis due to product gas evolution. Consequently, heat transfer into the catalytic fixed-bed exhibits a pronounced local dependency. For a better understanding of such multiphase dehydrogenation systems, we have performed heat transport measurements in the presence of the chemical reaction, namely during the dehydrogenation of perhydro benzyltoluene (H12-BT) and perhydro dibenzyltoluene (H18-DBT). The results reveal that overall heat transfer coefficients show a clear local dependency on the axial coordinate. Moreover, the two carriers were found to differ significantly in their thermal behavior. Based on a global analysis, two main regimes can be distinguished in the dehydrogenation reactor: 1.) With the LOHC mixture being primarily in the liquid phase, heat transport is dominated and intensified by the hydrogen release; 2.) With an increasing proportion of LOHC vapor in the reactor, the heat transport is dominated by the gas phase, resulting in significantly lower thermal parameters.