Dehydrogenation Kinetics and Catalysis for Hydrogen Recovery From Organic Heteroaromatic Compounds for Hydrogen Storage

The kinetics of the dehydrogenation of dodecahydro-N-ethylcarbazole and dodecahydrocarbazole over a Pd/SiO2 catalyst is reported at 170 ºC and 1 atm. The dehydrogenation of dodecahydro-N-ethylcarbazole proceeded to complete conversion and hydrogen recovery (5.8 wt %) with an initial TOF three times that of dodecahydrocarbazole dehydrogenation. The lower TOF for dodecahydrocarbazole was attributed to the strong adsorption of the dehydrogenated products to the metal surface through the N atom. The effect of Pd particle size on the TOF and selectivity of the dodecahydrocarbazole dehydrogenation reactions was also studied. Decreasing the particle size increased the TOF and selectivity to the completely dehydrogenated product. The effect of the ethyl group on the adsorption energies of dodecahydro-N-ethylcarbazole and its dehydrogenated products was studied using density functional theory (DFT). The DFT results provide insight into the reaction mechanism of dodecahydro-N-ethylcarbazole dehydrogenation and the significant difference in H2 recovery compared to dodecahydrocarbazole.