Preparation Of Ni - Based Metal Catalysts And Their Catalytic Hydrogen Production For Hydrazine Hydrate

Hydrogen is one of clean energy sources, it can lead to zero carbon emissions and its application in hydrogen fuel cell can greatly improve the efficiency of energy conversion. The development and utilization of hydrogen has an important significance in the current situation of energy crisis and environmental deterioration. Hydrazine hydrate (N2H4·H2O) is a high hydrogen-containing compound (12.5 wt%), its completely decomposed products are only hydrogen and nitrogen other than hazardous by-products. The application of hydrazine hydrate has a bright future, and the key to control decomposition of hydrazine hydrate is developing a highly efficient catalyst.In this paper, the hydrazine decomposition catalysts with different Ni/CeO2 ratio were synthesized by liquid co-reduction in normal temperature and pressure, using nickel chloride and cerium chloride as precursors, sodium borohydride as the reducing agent. The factors affecting the decomposition of hydrazine hydrate by catalysts were tested, include ratio of Ni/CeO2, concentration of sodium hydroxide, temperature and others. The results of tests show that:which the molar ratio of the Ni/CeO2 in catalyst is 9:1 performed the best catalytic properties, with the concentration of sodium hydroxide greater than or equal 0.5mol/L, and the reaction temperature is 70℃in catalytic reaction system:the hydrogen selectivity of Ni9-CeO2 catalyst decompose hydrazine hydrate is above 99%, the turnover frequency is 50.Oh-1. The characterization of Ni9-CeO2 catalyst show configuration is face-centered cubic of nickel crystal, the crystal size is 21.8nm, the body of catalyst is porous structure and can be dispersed in aqueous phase reaction solution. Cerium oxide can not only prevent massive agglomeration of nickel nanoparticles, but has a synergy with nickel, it play an important role on improving the hydrogen selectivity and conversion frequency of catalyst.On the base of Ni-CeO2 catalyst, the NiMo-CeO2 catalysts with different amounts of molybdenum were synthesized by the same method. The factors affecting the decomposition of hydrazine hydrate by catalysts were tested, include ratio of Ni/Mo/Ceria, concentration of sodium hydroxide, temperature and others. The results show that:which the molar ratio of the Ni/Mo/CeO2 in catalyst is 9:2:1 performed the best catalytic property, with the concentration of sodium hydroxide greater than or equal 0.5mol/L, and the reaction temperature is 70℃ in catalytic reaction system:the hydrogen selectivity of Ni9Mo2-CeO2 catalyst decompose hydrazine hydrate is above 99%, the turnover frequency is 65.5h-’. The characterization of Ni9Mo2-CeO2 catalyst show the configuration of catalyst is face-centered cubic of nickel crystal, the crystal size is 10.4nm, the body of catalyst is irregular particles, which can be dispersed and suspended in an aqueous phase reaction solution. The adding of appropriate amount of molybdenum in the catalyst could reduced crystal particle size of catalyst by interference crystallization, but also prevent aggregation of nanoparticles to improve the dispersion of catalyst, increased the number of active site, thereby enhanced the catalytic activity; but excessive molybdenum in catalyst granule cause the form of plate, resulted the reduction of catalytic activity.In the catalytic reaction test, sodium hydroxide created a strong alkaline environment for the catalytic decomposition of hydrazine, the OH-1 in the aqueous phase reaction solution prevent the side reactions of decomposition of hydrazine generates ammonia (NH3), improve the selectivity of the catalyst, but also prevent the occurrence of the reverse hydrolysis of hydrazine hydrate to accelerate catalytic reaction process.