Enhancing the power density of hydrogen release from LOHC systems by high Pt loadings on hierarchical alumina support structures

In this contribution, a step change in the power density of hydrogen release from LOHC systems is presented. This could be achieved by the use of hierarchical alumina supports in combination with high Pt loadings. Here, a demonstration was carried out for the catalytic dehydrogenation of perhydro dibenzyltoluene (H18-DBT). In the course of our study, different alumina support materials were characterized and loaded with 0.3, 0.6, 0.9 and 1.2 wt% Pt , respectively. It was found that a specific bimodal pore structure with a large pore volume in both, the mesoporous range between 10 and 25 nm and the macroporous range between 500 and 1000 nm, enabled high Pt-based productivities even at Pt loadings, four times higher than that of the current technical standard. This gives access to a substantially improved volumetric power density of the respective catalyst. In batch dehydrogenation experiments with a 1.5 mm pellet and a Pt loading of 0.9 wt% Pt , a doubling of volumetric power density could be achieved compared to the technical 0.3 wt% Pt standard material (Clariant, Elemax D102). Our analytical work elucidated that this highly relevant increase can be related to a faster mass transfer resulting from the special pore structure of the catalyst support and to a better Pt distribution on the support resulting in a thinner egg-shell layer. Using the optimized catalyst materials in continuous fixed-bed dehydrogenation experiments higher gas hold-up in the reactor and dewetting of the catalyst surface become additional aspects that influence the overall observed catalyst performance. • Improved catalysts increase power density of LOHC dehydrogenation reactors. • Bimodal supports enable higher Pt loadings and volumetric catalyst productivities. • Mesopores are necessary to disperse Pt nanoparticles. • Macropores allow faster mass transport and facilitated hydrogen bubble nucleation. • A 200% increase in volumetric productivity was achieved with the new catalyst.