Preparation And Performance Investigation Of Catalysts For Degradation Or Hydrogen Generation Of Hydrazine Hydrate

Hydrazine?H₂NNH₂?and hydrazine hydrate??H₂NNH₂·H₂O??are widely used in the field of fine chemicals.It is inevitable that there will be a large amount of wastewater containing hydrazine that needs to be treated to meet environmental requirements during their production and application.On the other hand,safe and efficient storage and release of hydrogen is a key challenge in the future.Hydrazine hydrate has attracted considerable attention as a safe chemical hydrogen-storage material with 8.0wt%high hydrogen density.Therefore,it is of great value to study the efficient degradation and hydrogen generation of hydrazine hydrate through catalyst catalysis.First,three copper-based heterogeneous catalysts for the oxidative degradation of hydrazine hydrate in diluted aqueous solution with oxygen as oxidant were prepared.The oxidative degradation results revealed that the trimetallic catalyst c-CuZnCr exhibited good performance compared to both the neat CuO?c-Cu?and the bimetallic catalyst c-CuZn.When 23 mg of c-CuZnCr was applied to the oxidative degradation 200 mL of aqueous hydrazine hydrate with a concentration of 0.2%,the degradation rate reached up to 99.96%under atmospheric pressure of oxygen at room temperature in 360 min.The catalysts were characterized by XRD,XPS,SEM,ICP-OES and N₂ adsorption-desorption methods.The characterization results disclosed that the copper?II?ion Cu²⁺on the surfaces of the catalysts were the active species for all the three catalysts,and the high activity of c-CuZnCr was due to its bigger surface area from the doping of Zn and Cr into CuO.Kinetic study revealed that the activation energy of the reaction over the c-CuZnCr catalyst was 32.73 kJ·mol^-1.The reaction was shown to be 0.97 and 0.78 orders with respect to the hydrazine hydrate concentration and the pressure of oxygen,respectively.Second,well-dispersed Ni-CeO_x nanocomposites grown on the surface of carbon nanotubes?CNTs?were successfully synthesized via a simple one-step co-reduction method.The structure and properties of the catalysts were studied by XRD,XPS,SEM,TEM and ICP-OES.Among the prepared catalysts Ni-?CeO_x?_0.5/CNTs exhibited the highest catalytic activity,with 100%hydrogen selectivity and 80 h^-1of TOF for hydrogen generation from hydrazine hydrate under 1.0 M NaOH solution at 343 K.This superior catalytic performance was attributed to the synergistic effect between Ni and CeO_x,ultrafine and well-dispersed of Ni-CeO_x nanocomposites,as well as a strong metal–support interaction between Ni-CeO_x and the CNTs.