Reversible hydrogenation and dehydrogenation of benzene for hydrogen storage on highly dispersed Pd/γ-Al2O3 catalyst

The research and development of efficient catalyst is the key to achieving high-capacity hydrogen storage in liquid organic hydrogen carriers (LOHCs). The highly dispersed Pd/γ-Al2O3 catalysts with few-atom Pd were prepared by impregnation method using HNO3 as promoter. The hydrogen storage capacity of the benzene/cyclohexane hydrogen carriers was further investigated by vapor phase benzene hydrogenation and cyclohexane dehydrogenation reactions over the studied Pd/γ-Al2O3 catalysts. The results showed that the metal Pd was the active centers for the benzene hydrogenation/cyclohexane dehydrogenation reactions. The addition of HNO3 can effectively promote the metal Pd to be highly dispersed, thus improving the Pd atoms utilization and reducing the Pd dosage. Meanwhile, the strongly electronic effects between the highly dispersed Pd species and the Al2O3 support promoted the electron-deficient Pdδ+ sites to be formed, which enhanced the adsorption and activation ability for the reactants molecules. The benzene conversion on the Pd/γ-Al2O3 catalyst with a metallic Pd loading of 1.0 wt% reached 97.51 % at 200 °C. While the cyclohexane conversion reached 90.94 % at 400 °C with the actual hydrogen storage capacity of 6.54 wt%, which provided an effective idea for large-scale storage and transportation of H2 based on LOHCs.