Tuning the Interaction between Pd and MgAl₂O₄ To Enhance the Dehydrogenation Activity and Selectivity of Dodecahydro-N-ethylcarbazole

The liquid organic hydrogen carrier (LOHC) technology is one of the most promising technologies in hydrogen storage and delivery. As one of the most promising hydrogen storage carriers, N-ethylcarbazole (NEC) can reversibly undergo hydrogenation and dehydrogenation reactions below 473 K. However, it is prone to the side reaction of the C-N bond cleavage during the dehydrogenation reaction because the dehydrogenation products are difficult to desorb from the active site. Herein, we found that the active metal Pd catalyst supported on the Mg-Al spinel can reduce the occurrence of side reactions, improve the dehydrogenation activity and the selectivity of NEC, and reduce the loading of noble metal Pd. As revealed by various catalyst characterizations, the improvement of catalyst activity is related to the smaller active metal particles and the valence distribution of Pd. The weakening of the C-N bond cleavage reaction is related to the catalyst with moderate acid site density, the synergy effect between metal sites and acid sites, and the weak adsorption capacity of dehydrogenation products. This study provides an idea for the design of highly active and selective dehydrogenation catalysts.