Study On The Hydrogen Uptake And Release Performance Of Carbazole

Carbazole is one of the nitrogen-substituted organic heteroaromatic compounds with hydrogen storage capacity6.7%when completely hydrogenated, making it possible candidates for hydrogen storage.In the present work, hydrogenation reaction of carbazole over the Raney-Ni catalyst was investigated. It is clearly proved that solvent, temperature, pressure and the dosage of catalyst have distinct effect on the hydrogen uptake properties of carbazole. The amount of absorbed hydrogen showed the trend of first increase and then decrease with the rise of temperature in the range of170℃-270℃,and reached maximum at250℃; With the rise of the reaction pressure, the amount of absorbed hydrogen increased; Catalyst dosage significantly affected the hydrogen absorbing amount in low dosage range; The amount of absorbed hydrogen could achieve a considerable optimum under the condition of250℃,5MPa and0.5g Raney-Ni when the ratio of Carbazole/Declain was1/5.9.The GC/MS analysis of the liquid samples from the hydrogenation reactions confirmed the main production of tetrahydrocarbazole, dodecahydrocarbazole and small amounts of hexahydrocarbazole and octahydrocarbazole. Using Gaussian, the optimized geometric configuration of carbazole and the intermediate compounds were obtained. The thermal energy was calculated using density functional theory (DFT).The dehydrogenation of products from hydrogenation was studied over the Pd/C catalyst. The dehydrogenation reaction conversion accelerates with increased temperature, proceeding a maximum recovery of the stored H2at220℃. However, when the temperature increases further, the hydrogen uptake decreased. At220℃, an appropriate60.5%recovery of the stored H2can be obtained with3ml reagent and11.1wt%catalyst. The main dehydrogenated products are tetrahydrocarbazole and carbazole.Finally, the present work intrduced the research on the preparation of Pd/Al2O3catalyst and tested the catalytic performance by carrying out the experiments on the dehydrogenation of tetrahydrocarbazole.1.12wt%Pd/Al2O3has been found to be an efficient catalyst for the dehydrogenation of tetrahydrocarbazole with a conversion rate75.1%at220℃.