Hydrogenation of ethylene over lanthanum-nickel (LaNi5) alloy

High catalytic performance of Al-Pd-(Ru, Fe) icosahedral approximants for acetylene semi-hydrogenation

Three cubic crystalline icosahedral approximants (C phase: Al_72.0Pd_16.4Fe_11.6, P₄₀ phase: Al_72.0Pd_16.4Ru_11.6, P₂₀ phase: Al_70.0Pd_22.3Ru_7.7) exhibit high ethylene selectivity of over 90% for hydrogenating acetylene at 150 °C. Moreover, the powdered P₂₀ also demonstrates a high catalytic performance under an industry-like ethylene feed containing 0.5% acetylene as an impurity. Overall, icosahedral approximants in the Al–Pd–(Ru, Fe) systems are promising as a novel class of alloy catalysts.

The Al–Pd–(Ru, Fe) icosahedral approximants exhibited high catalytic ethylene selectivity and stability for semi-hydrogenation of acetylene.

MgH2/CuxO Hydrogen Storage Composite with Defect-Rich Surfaces for Carbon Dioxide Hydrogenation

Thermal conversion of CO₂ to value-added chemicals is challenging due to the extreme inertness of the CO₂ molecule and the low selectivity of products. We reported a defect-rich MgH₂/Cu_xO hydrogen storage composite from mechanochemical ball-milling for the catalytic hydrogenation of CO₂ to lower olefins. The defect-rich MgH₂/Cu_xO hydrogen storage composite achieves a C₂⁼-C₄⁼ selectivity of 54.8% and a CO₂ conversion of 20.7% at 350 °C under a low H₂/CO₂ ratio of 1:5, which increases the efficiency of H₂ utilization by offering lattice H^- species for hydrogenation. Density functional theory calculations show that the defective structure of MgH₂/Cu_xO can promote CO₂ molecule adsorption and activation, while the electronic structure of MgH₂ is beneficial for offering lattice H^- for CO₂ molecule hydrogenation. The lattice H^- can combine the C site of CO₂ molecule to promote the formation of Mg formate, which can be further hydrogenated to lower olefins under a low H^- concentration. This work for CO₂ conversion by a defect-rich MgH₂/Cu_xO hydrogen storage composite can inspire the catalysts design for the hydrogenation of CO₂ to lower olefins.

Ability of hydrogen storage CeNi5-x Ga x and Mg2Ni alloys to hydrogenate acetylene

Hydrogen storage properties and reactivity for hydrogenation of acetylene in a series of CeNi_5-x Ga _x (x = 0, 0.5, 0.75, 1, 1.25, 1.5) alloys and Mg₂Ni were determined and compared. The structure of CeNi₅ (CaCu₅ type) was maintained up to CeNi_3.5Ga_1.5 when Ni was replaced by Ga. The replacement facilitated hydrogenation absorption by creating larger interstitial spaces through expansion of the lattice, allowing CeNi_4.25Ga_0.75 to absorb the greatest proportion of hydrogen atoms among the alloys under the same conditions. The results showed that the absorbed hydrogen in CeNi_3.75Ga_1.25 improved reactivity. In contrast, Mg₂Ni formed a hydride upon hydrogenation of acetylene and thus possessed much lower activity. The difference of the activity of absorbed hydrogen between CeNi_5-x Ga _x and Mg₂Ni was confirmed from transient response tests under reaction gases alternately containing He and H₂.

Thermochemical Energy Storage through De/Hydrogenation of Organic Liquids: Reactions of Organic Liquids on Metal Hydrides

A study of the reactions of liquid acetone and toluene on transition metal hydrides, which can be used in thermal energy or hydrogen storage applications, is presented. Hydrogen is confined in TiFe, Ti0.95Zr0.05Mn1.49V0.45Fe0.06 ("Hydralloy C5"), and V40Fe8Ti26Cr26 after contact with acetone. Toluene passivates V40Fe8Ti26Cr26 completely for hydrogen desorption while TiFe is only mildly deactivated and desorption is not blocked at all in the case of Hydralloy C5. LaNi5 is inert toward both organic liquids. Gas chromatography (GC) investigations reveal that CO, propane, and propene are formed during hydrogen desorption from V40Fe8Ti26Cr26 in liquid acetone, and methylcyclohexane is formed in the case of liquid toluene. These reactions do not occur if dehydrogenated samples are used, which indicates an enhanced surface reactivity during hydrogen desorption. Significant amounts of carbon-containing species are detected at the surface and subsurface of acetone- and toluene-treated V40Fe8Ti26Cr26 by X-ray photoelectron spectroscopy (XPS). The modification of the surface and subsurface chemistry and the resulting blocking of catalytic sites is believed to be responsible for the containment of hydrogen in the bulk. The surface passivation reactions occur only during hydrogen desorption of the samples.