Browsing by Author "de Nooijer, Niek"
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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 Influence of H2S on the hydrogen flux of thin-film PdAgAu membranes(2020-03-04) de Nooijer, Niek; Sanchez, Julio Davalos; Melendez, Jon; Fernandez, Ekain; Pacheco Tanaka, David Alfredo; van Sint Annaland, Martin; Gallucci, Fausto; Tecnalia Research & Innovation; TECNOLOGÍAS DE HIDRÓGENO; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOSPd-based membranes have the potential to be used for hydrogen purification and production in membrane reactors. However, the presence of impurities in the feedstock, such as H2S can poison the membrane, thus decreasing the hydrogen permeation by blocking and deactivating active sites of the Pd-alloy on the membrane surface. H2S at high concentrations can even destroy the membrane by the formation of Pd4S. It is known that alloying of Pd with Au enhances the membrane resistance to H2S. This work reports the performance of six PdAgAu/Al2O3 supported membranes, prepared by electroless plating combined with PVD under exposure to trace amounts (<2 ppm) of H2S. The Au content shows not to play a significant role at these low concentrations. Exposure results suggest a dual influence of physisorbed H2S and chemisorbed S species. A Langmuir description shows that the influence of the partial pressure of hydrogen is negligible on the flux inhibition. In the post characterization the absence of Pd4S was shown, however the surface was affected by the exposure to H2S.Item On concentration polarisation in a fluidized bed membrane reactor for biogas steam reforming: modelling and experimental validation: Modelling and experimental validation(2018-09-15) de Nooijer, Niek; Gallucci, Fausto; Pellizzari, Emma; Melendez, Jon; Pacheco Tanaka, David A.; Manzolini, Giampaolo; van Sint Annaland, Martin; Tecnalia Research & Innovation; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOSThe production of pure hydrogen through the steam reforming of biogas in a fluidized bed membrane reactor has been studied. A phenomenological one-dimensional two-phase fluidized bed reactor model accounting for concentration polarisation with a stagnant film model has been developed and used to investigate the system performance. The validation of the model was performed with steam reforming experiments at temperatures ranging from 435 °C up to 535 °C, pressures between 2 to 5 bar and CO2/CH4 ratios up to 0.9. The permeation performance of the ceramic-supported PdAg thin-film membrane was first characterized separately for both pure gas and gas mixtures. Subsequently, the membrane was immersed into a fluidized bed containing Rh supported on alumina particles and the reactor performance, viz. the methane conversion, hydrogen recovery and hydrogen purity, was evaluated under biogas steam reforming conditions. The resulting hydrogen purity under biogas steam reforming conditions was up to 99.8%. The model results were in very good agreement with the experimental results, when assuming a thickness of the stagnant mass transfer boundary layer around the membrane equal to 0.54 cm. It is shown that the effects of concentration polarisation in a fluidized bed membrane reactor can be well described with the implementation of a film layer description in the two-phase model.