Examinando por Autor "Madeira, Luis M."

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Effect of ceria particle size as intermediate layer for preparation of composite Pd-membranes by electroless pore-plating onto porous stainless-steel supports
(Elsevier, 2023) Macedo, M. Salomé; Acha Uriarte, N.; Soria, M.A.; Madeira, Luis M.; Calles, J.A.; Sanz, R.; Alique, D.
The use of H2-selective membranes for ultra-pure H2 production has been assigned as an attractive technology, particularly those based on Pd-films deposited onto porous stainless-steel (PSS) supports. The ability to incorporate thin Pd-films with enough adherence on any internal or external surfaces becomes essential to minimize their complexity and cost while improving their performance. The modification of original PSS substrates with diverse intermediate layers, especially those made of ceria, is presented as a promising alternative. In this context, the current study addresses for the first time the use of different CeO2 particle sizes to generate an intermediate layer and facilitate the subsequent generation of a thin Pd-film by electroless pore-plating (ELP-PP). The membrane containing the smallest CeO2 particle size (membrane S) demonstrated the lowest performance, which was assigned to the high compaction of the material and generation of cracks on its surface during calcination that consequently led to the deposition of a greater amount of Pd. On the other hand, the morphology of membranes M (medium CeO2 particle size) and L (large CeO2 particle size) were very similar, although the first one demonstrated a slightly smaller interparticle porosity, which led to the deposition of a more homogeneous and thinner Pd-film. Therefore, an outstanding performance in terms of H2 permeance (5.98 × 10− 4 mol⋅m− 2 ⋅s − 1 ⋅Pa− 0.5 at 400 ◦C) was obtained for this membrane. Permeation tests with binary mixtures (H2-N2, H2-CO2, or H2-CO) revealed a concentration-polarization effect in all cases, as well as a certain inhibition effect in the presence of CO. Finally, it should be highlighted the high stability of the membranes during the entire set of experiments, independently of the considered particle size. Thus, enough mechanical and thermal resistances can be assured for future applications.
Thermodynamic Comparison between Conventional, Autothermal, and Sorption-Enhanced Bio-oil Steam Reforming
(American Chemical Society, 2025-01-10) Megía, Pedro J.; Rocha, Claudio; Vizcaíno, Arturo J.; Carrero, Alicia; Calles, José A.; Madeira, Luis M.; Soria, Miguel A.
This study presents a comprehensive thermodynamic analysis comparing three bio-oil steam reforming processes: traditional steam reforming, autothermal reforming, and sorption-enhanced steam reforming. Using Aspen Plus V12.1 software, simulations were performed to evaluate the hydrogen production, energy requirements, and influence of key process variables such as the temperature, pressure, or steam-to-carbon ratio. While traditional steam reforming is capable of achieving high hydrogen production, it requires substantial external energy input to drive forward the reaction, given the endothermic nature of the reactions. In comparison, autothermal reforming allows thermally neutral conditions by integrating endothermic steam reforming with exothermic partial oxidation reactions. Although the energy requirements significantly decrease, it also leads to lower hydrogen yields due to its consumption in the oxidation processes. In contrast, sorption-enhanced steam reforming improves hydrogen production compared to the other configurations ascribed to the in situ CO2 capture by using sorbents that shift the equilibrium toward hydrogen with purities over 98%, thus minimizing the need for additional gas separation processes apart from reducing the CO and CH4 formation. Additionally, the exothermic nature of the CO2 capture reactions contributes to reducing the energy requirements or even generates excess energy at certain conditions that can be used as a heat source. The bio-oil composition showed minor variations in hydrogen yields, making these findings applicable to different bio-oil compositions