Browsing by Author "Arias, P. L."
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Item Effect of Au addition on hydrogen permeation and the resistance to H2S on Pd-Ag alloy membranes(2017) Melendez, Jon; de Nooijer, Niek; Coenen, Kai; Fernandez, Ekain; Viviente, Jose Luis; van Sint Annaland, Martin; Arias, P. L.; Tanaka, D. A.Pacheco; Gallucci, Fausto; Tecnalia Research & Innovation; TECNOLOGÍAS DE HIDRÓGENO; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOSIn order to make a detailed comparison between Pd-Ag and Pd-Ag-Au membranes according to their H2 permeation properties and sulfide resistance Au was deposited by the electroless plating (ELP) technique onto one half of Pd-Ag membranes. Membranes' thicknesses are ranged between 2.45 and 3.13 µm. Permeation tests have been carried out from 400 to 600 °C under single gas conditions. The Pd91.7Ag4.8Au3.5 membrane has shown a H2 permeance of 4.71·10−3 mol s−1 m−2 Pa0.5 at 600 °C, which is one of the highest values ever reported in the literature, where the Pd-Ag-Au membranes have exhibited higher hydrogen permeation rates compared to their respective Pd-Ag membranes above 550 °C. The H2 permeation properties have been determined in terms of the degree of H2S inhibition, up to 17 ppm, and subsequent H2 flux recovery rate. Pd-Ag membranes alloyed with gold resisted 12.5 h of H2S exposure showing recovery rates of 85% and 83% for Pd91.5Ag4.7Au3.8 and Pd90.5Ag4.6Au4.9 membranes, respectively, whereas the hydrogen flux of non-gold membranes decreased below detectable values. H2/N2 ideal perm-selectivity of the Pd-Ag membrane was reduced to 18 after H2S tests (starting from > 1308) while Pd-Ag-Au membranes showed a better resistance to sulfur with H2/N2 selectivity values of 793 and 121 (starting from > 4115 and > 2557 respectively). No evidence of the formation of a crystalline sulfide phase on the Pd-Ag-Au alloy membrane surfaces was found in the XRD patterns after H2S exposure and also XPS characterization did not show important changes in the composition before and after the H2S exposure tests. However, SEM images showed a decrease in the thickness of the Pd-Ag membrane and signs of corrosion and roughening on its surface, while gold-alloyed membranes did not show any damage.Item Natural and synthetic iron oxides for hydrogen storage and purification(2013-07) Requies, J.; Güemez, M. B.; Perez Gil, S.; Barrio, V. L.; Cambra, J. F.; Izquierdo, U.; Arias, P. L.; VALORIZACIÓN DE RESIDUOSIn this paper, the hydrogen storage capacity of some synthetic and natural iron oxides is presented. The results of the activity tests and characterization techniques of natural and synthetic iron oxides (N2 adsorption-desorption isotherms, temperature-programmed reduction, X-ray diffraction, and plasma atomic emission spectroscopy) suggest that the use of chromium on iron oxide systems improved their hydrogen storage capacity. This is related to the capacity of chromium to modify the iron oxide reduction profile when Cr was incorporated. A direct reduction from Fe3O4 to Fe was observed as the mechanism for H2 storage. In addition, natural oxides as commercial Superfine and Densinox-L oxides are proved to be suitable materials to store and purify H2 due to their high stability during different cycles of reduction and oxidation. The best results among the natural ones were Densinox-L and among the synthetic ones Fe-10Cr.Item Preparation and characterization of ceramic supported ultra-thin (~1 µm) Pd-Ag membranes(2017) Melendez, Jon; Fernandez, Ekain; Gallucci, Fausto; van Sint Annaland, Martin; Arias, P. L.; Pacheco Tanaka, David A.; Tecnalia Research & Innovation; TECNOLOGÍAS DE HIDRÓGENO; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOSThis work reports the preparation and characterization of ultra-thin (~1 µm thick) Pd-Ag supported membranes for hydrogen purification. Ultra-thin membranes with different thicknesses (ranging from 0.46 to 1.29 µm) have been prepared by electroless plating (ELP) technique onto asymmetric tubular porous alumina supports. The membranes have been characterized by single gas and mixed gas permeation experiments at temperatures between 300 and 500 °C obtaining a correlation for the membrane permeation as a function of the activation energy and the membrane thickness. Hydrogen permeation results of the ultra-thin Pd-Ag membranes have been compared with other highly permeable membranes reported in the literature and they show some of the highest H2permeance values. A 1.29 µm thick membrane has been tested for 1000 h at 400 °C and has shown a stable H2permeance of 9.0−9.4×10−6mol m−2s−1Pa−1with a H2/N2perm-selectivity between 3300 and 2000 at 100 kPa transmembrane pressure difference. The same membrane has been tested with a feed gas mixture of H2/N2/CO with a 15% CO content and H2binary mixtures containing N2, CH4and CO2. When tested in a catalyst fluidization environment during 100 h, the 1.29 µm thick membrane showed stable H2permeance and H2/N2perm-selectivity.