Papers by Keyword: Hydrogen Storage Material

Abstract: Large amounts of depleted uranium kept as uranium fluoride or solid form after enrichment of natural uranium is sought to be utilized in the form of UNiAl intermetallic compound for hydrogen absorber. First principles calculation on UNiAl hydride has been performed in this study to predict the change of the crystal structure and the lattice constants with varying the hydrogen content. The results of the calculations have supported the experimental trends, suggesting that the present approach is promising in predicting the better hydrogen absorber based on depleted uranium.

Abstract: A novel hydrogen storage material Mg₂Ni has been studied by the first-principle methods based on plane-wave pseudopotential theory. The corresponding electronic structure of hydrogen storage materials, Mg₂Ni, Mg₁₂Ni₅M₁ (M = Mn and Cu), and their hydride have also been investigated. The enthalpy of hydrogenation reaction is-65.07kJ/mol (H₂), which is in line with the experimental results. The stability of the new hydride alloy increased by substitution with Cu, and a small amount of alternative might be preventing powdering after several cycles. The Mn atom substitutes Ni atom of hydride alloy which would weaken the H-Ni bond, and the temperature of desorption decreased. The results will play an important role in practical application.

Abstract: Mg-based hydrogen storage material was prepared by ball milling, and then the material was used to react with CS₂. The morphology and hydrogen desorption properties of the hydrogen storage material as well as the CS₂ hydrogenation product were analyzed. Results show that in situ hydrogenation and desulfurization of CS₂ happens with the MgH₂ in the hydrogen storage material as hydrogen donator and desulfurizer at 300 °C and ordinary pressure, and MgS, CH₄ and H₂S are generated from the reaction. There is a coupling relationship between dehydrogenation of the hydrogen storage material and hydrogenation of CS₂. The addition of nickel and molybdenum show negative effect on the sulfur fixation capability of the Mg-based hydrogen storage material though they could decrease the dehydrogenation temperature of the material.

Abstract: Magnesium-based hydrogen storage materials were prepared by reactive milling of magnesium under hydrogen atmosphere with crystallitic carbon, prepared from anthracite coal, as milling aid. The XRD analysis shows that in the presence of 30 wt.% of crystallitic carbon, the Mg easily hydrided into β-MgH₂ of crystal grain size 29.7 nm and a small amount of γ-MgH₂ after 3 h of milling under 1 MPa H₂. The enthalpy and entropy changes of the hydrogen desorption reaction are 42.7 kJ/mol and 80.7 J/mol K, respectively, calculated by the vant Hoff equation from the p-C-T data in 300-380°C.

Abstract: Magnesium-based hydrogen storage powders were prepared by reactive milling under hydrogen atmosphere. The crystallitic carbon, prepared from anthracite coal by demineralization and carbonization, was used as milling aid and synergic hydrogen storage additive of magnesium. Dispersive powders of particle size about 20 to 60 nm and hydrogen capacity of 4.78 wt.% were prepared from magnesium with 40 wt.% of crystallitic carbon by 3 h of milling under 1 MPa of hydrogen atmosphere. The hydrogen stored in carbon increased with the addition of Al, Mo, Co and Fe. FT-IR showed that the carbon atoms at the edges of crystallitic carbon particles were hydrogenated into C-H during reactive milling with hydrogen. The initial dehydrogenation temperature of hydrogen-storage material 60Mg40C is 275.8 °C, and its dehydrogenation plateau pressure at 300 °C is 0.2 MPa and the length of the plateau is 5.0 wt.% of hydrogen capacity.

Abstract: The hydrogenation of preasphaltene (PA), from Chinese Xiaolongtan lignite liquefied heavy product, was investigated with hydrogen storage materials in a batch autoclave. The effects of reaction conditions such as hydrogen storage materials and temperature on the yields of gas+oil, asphaltene, char and the conversions of preasphaltene were discussed. Preliminary studies indicate that increasing temperature not only improves hydrogen donor performance of hydrogen storage materials but also enhances conversion of feedstock PA and gas+oil yield. The conversion of PA and the yield gas+oil get to 72.02% and 41.46%, respectively, under 5% MgH₂, 5MPa initial hydrogen pressure, temperature 420°C and reaction time 30min. Meanwhile MgH₂ is stronger than NaBH₄ in hydrodeoxygenation of PA under the same conditions. Elemental and FTIR analyses were used to illustrate the structural characteristics of feedstock PA and remaining preasphaltene (RPA).