169 research outputs found

    Redox dynamics of sulphur with Ni/GDC anode during SOFC operation at mid- and low-range temperatures: An operando S K-edge XANES study

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    Sulphur poisoning of nickel-based solid oxide fuel cell (SOFC) anode catalysts is a well-documented shortcoming, but not yet fully understood. Here, a novel experiment is demonstrated to obtain spectroscopic information at operando conditions, in particular the molecular structure of sulphur species in the sulphur K-shell X-ray absorption near edge structure (XANES) region for a SOFC anode under realistic operando conditions, thus, with the flux of O2- from cathode to anode. Cooling from T = 550 degrees C stepwise down to 250 degrees C, 5 ppm H2S/H-2 reacting with Ni-gadolinium doped ceria (GDC) anode resulted in several sulphur species in different oxidation states (6+, 4+, 0, -2) and in amounts being at a minimum at high temperature. According to sulphur speciation analysis, the species could either relate to -SO42- or SO3 (g), -SO32- or SO2 (g), S-2 (g) or surface-adsorbed S atoms, and, Ni or Ce sulphides, respectively. The coexistence of different sulphur oxidation states as a function of temperature was analysed in the context of thermodynamic equilibrium calculations. Deviations between experimental results and calculations are most likely due to limitations in the speed of some intermediate oxidation steps as well as due to differences between stoichiometric CeO2 used in calculations and partially reduced Ce0.9Gd0.1O2-delta. (C) 2013 Elsevier B.V. All rights reserved

    Integrated management of ash from industrial and domestic combustion : a new sustainable approach for reducing greenhouse gas emissions from energy conversion

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    This work supports, for the first time, the integrated management of waste materials arising from industrial processes (fly ash from municipal solid waste incineration and coal fly ash), agriculture (rice husk ash), and domestic activities (ash from wood biomass burning in domestic stoves). The main novelty of the paper is the reuse of wood pellet ash, an underestimated environmental problem, by the application of a new technology (COSMOS-RICE) that already involves the reuse of fly ashes from industrial and agricultural origins. The reaction mechanism involves carbonation: this occurs at room temperature and promotes permanent carbon dioxide sequestration. The obtained samples were characterized using XRD and TGA (coupled with mass spectroscopy). This allowed quantification of the mass loss attributed to different calcium carbonate phases. In particular, samples stabilized using wood pellet ash show a weight loss, attributed to the decomposition of carbonates greater than 20%. In view of these results, it is possible to conclude that there are several environmental benefits from wood pellet ash reuse in this way. In particular, using this technology, it is shown that for wood pellet biomass the carbon dioxide conversion can be considered negative

    Recent advances in catalytic hydrogenation of carbon dioxide

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