Continuous hydrogenation of N-ethylcarbazole in a micro-packed bed reactor for hydrogen storage

N-ethylcarbazole is a promising alternative for liquid organic hydrogen carriers. However, due to the high kinetic barriers in N-ethylcarbazole hydrogenation, harsh conditions and high loading of Ru metal are needed. Designing a cost-effective and low-temperature hydrogenation process for liquid organic hydrogen carriers remains a significant challenge. In this work, a continuous hydrogenation process of N-ethylcarbazole in a micropacked bed reactor is reported. The effects of catalysts, temperature, hydrogen pressure, and gas flow rate are evaluated. The results show that 1 wt% Ru/Al2O3 exhibits the best catalytic performance with 100 % conversion of N-ethylcarbazole, 99.41 % selectivity to dodecahydro-N-ethylcarbazole and 5.79 wt% mass hydrogen storage capacity under a mild reaction condition of 80 ℃ and 4 MPa. A kinetic model of N-ethylcarbazole hydrogenation is established and the network of stepwise hydrogenation reactions exhibits a good fit for each product. The hydrogenation of octahydro-ethylcarbazole is the rate-limiting step. The obtained kinetic model is helpful for process optimization of the continuous N-ethylcarbazole hydrogenation process.