An experimental investigation on the poor hydrogen sorption properties of nano-structured LaNi5 prepared by ball-milling

Nano-structured LaNi5 hydrogen storage materials prepared by ball-milling is analysed using differential scanning calorimetry (DSC) and x-ray photoelectron spectroscopy (XPS). DSC results indicate a partial elimination of defects at 500 °C in a more efficient way for the short-time ball-milled powders compared to the long-time ball-milled ones. XPS results show almost no change in the core-level electronic structure for La and Ni of LaNi5 in the bulk and the nano-structured forms, but gives an indication that the self-restoring mechanism of the active surface observed in the bulk sample (Siegmann et al. Phys. Rev. Lett. 40, 972) may not be occurring in the nano-powders. Results from the X-ray diffraction and the local structural studies together with the above observations suggest that the reduced unit-cell volume and the enhanced atomic disorder in the nano-structured LaNi5 cause a larger energy barrier for the hydrogen sorption reactions of the long-time ball-milled samples

HYDROTHERMAL LIQUEFACTION OF MICROALGAE IN THE PRESENCE OF HOMOGENEOUS AND HETEROGENEOUS CATALYSTS

The continuous raise in the prices of fossil fuels and the awareness of the society challenges related to their use has recently driven a strong growth of interest on the investigation of different biochemical or thermochemical processes for the production of liquid biofuels

Liquid hot water pretreatment of Arundo Donax: a comparison between batch and a flow-through systems

Lignocellulosic biomass is a valuable alternative raw material to partially substitute oil as both energy and chemical source. For example, polysaccharide constituents of lignocellulosic materials, hemicellulose and cellulose, can be hydrolytically depolymerized using acid catalysts or enzymes, while residual lignin can be used as a source of aromatic building blocks. The kinetic severity of the hydrolysis process can be adjusted to maximize alternatively the yields in fermentable sugars (bioethanol-way) or in chemicals such as furfural, hydroxymethylfurfural, levulinic acid. It is well known that, before performing the main hydrolysis step, a pretreatment stage of the matrix is necessary to cleave the bonds between hemicellulose, cellulose and lignin and to start breaking some of the polysaccharide chains. Liquid hot water (LHW) can be used for the pretreatment of biomass, without adding any acid to the system, thus avoiding the need of any subsequent neutralization step. In order to move toward industrial scale plant for production of energy and bulk chemicals from biomasses, continuous systems are desirable. An intermediate step toward the design of a continuous layout is constituted by semi-continuous processes. In this study, we have performed the LHW pretreatment of Arundo Donax (giant reed) in two different systems: a microwave (MW)-assisted batch reactor, where high heating rate can be achieved leading rapidly the system at the operative conditions of the pretreatment, and a fast heating flow-through layout in which the flow rate of the process water stream can be tuned. The achieved results highlight that in the microwave (MW)-assisted batch reactor good hemicelluloses solubilization, little sugar degradation and insignificant lignin and cellulose fractionation can be obtained by optimizing reaction temperature and time and that in the flow-through system high biomass conversion as well as very limited formation of degradation products can be obtained by adjusting the flow rate of the treatment water

Fundamental material properties of the 2LiBH4-MgH2 reactive hydride composite for hydrogen storage: (II) Kinetic properties

Reaction kinetic behaviour and cycling stability of the 2LiBH4-MgH2 reactive hydride composite (Li-RHC) are experimentally determined and analysed as a basis for the design and development of hydrogen storage tanks. In addition to the determination and discussion about the properties; different measurement methods are applied and compared. The activation energies for both hydrogenation and dehydrogenation are determined by the Kissinger method and via the fitting of solid-state reaction kinetic models to isothermal volumetric measurements. Furthermore, the hydrogen absorption-desorption cycling stability is assessed by titration measurements. Finally, the kinetic behaviour and the reversible hydrogen storage capacity of the Li-RHC are discussed.Fil: Jepsen, Julian. Helmholtz-Zentrum Geesthacht Zentrum für Material- und Küstenforschung; AlemaniaFil: Milanese, Chiara. Università degli Studi di Pavia; ItaliaFil: Puszkiel, Julián Atilio. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Helmholtz-Zentrum Geesthacht Zentrum für Material- und Küstenforschung; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Girella, Alessandro. Università degli Studi di Pavia; ItaliaFil: Schiavo, Benedetto. Università degli Studi di Palermo; ItaliaFil: Lozano, Gustavo A.. Helmholtz-Zentrum Geesthacht Zentrum für Material- und Küstenforschung; AlemaniaFil: Capurso, Giovanni. Helmholtz-Zentrum Geesthacht Zentrum für Material- und Küstenforschung; AlemaniaFil: Von Colbe, José M. Bellosta. Helmholtz-Zentrum Geesthacht Zentrum für Material- und Küstenforschung; AlemaniaFil: Marini, Amedeo. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Kabelac, Stephan. Leibniz Universität Hannover; AlemaniaFil: Dornheim, Martin. Helmholtz-Zentrum Geesthacht Zentrum für Material- und Küstenforschung; AlemaniaFil: Klassen, Thomas. Helmholtz-Zentrum Geesthacht Zentrum für Material- und Küstenforschung; Alemani