Catalytic hydrogenation and dehydrogenation performance of 9-ethylcarbazole as a liquid organic hydrogen carrier

The hydrogenation characteristics of 9-ethylcarbazole (9-ECZ) over Raney-Ni catalyst within the pressure range 0.2–0.8 MPa was investigated in this work. Initially, hydrogenation experiments were performed over various catalysts which revealed that 5 wt.% Ru/Al₂O₃ was the most active catalyst, whereas, Raney-Ni being least expensive was chosen for this study. Ten grams of 9-ECZ and 1 g of Raney-Ni were added to the stirrer type reactor, the effect of various parameters such as temperature, pressure, catalyst dosage, and stirring speed were examined. The results indicated that the optimal reaction temperature was 160 °C at a maximal pressure (0.8 MPa), stirring speed (800 rpm). Furthermore, 2 g of 9-ECZ was used with Raney-Ni dosages of 0.2 and 1.0 g and the corresponding hydrogen uptake was 5.16 wt.% and 5.81 wt.%, respectively. Lastly, three cyclic experiments were conducted to investigate the reversibility of the hydrogenation and dehydrogenation of 9-ECZ at 180 °C.