Dehydrogenation kinetics study of perhydro-N-ethylcarbazole over a supported Pd catalyst for hydrogen storage application

We report a kinetic study on dehydrogenation of perhydro-N-ethylcarbazole (12H-NECZ) over 5 wt% Pd/Al2O3 catalyst. Hydrogenation of N-ethylcarbazole (NECZ) was conducted at 8 Mpa and 180 °C and three isomers of 12H-NECZ was detected in the final hydrogenation products. The dehydrogenation kinetics of three isomers were studied in detail for the first time. The dehydrogenation of 12H-NECZ was found undergo three stages: perhydro-N-ethylcarbazole → octahydro-N-ethylcarbazole, octahydro-N-ethylcarbazole → tetrahydro-N-ethylcarbazole and tetrahydro-N-ethylcarbazole → N-ethylcarbazole. It is found that all three stages follow first-order kinetic processes with the activation energies of 56.3 kJ/mol, 59.2 kJ/mol and 73.1 kJ/mol respectively. The third step, 4H-NECZ → NECZ, was proved to be the rate limiting step.