Examinando por Autor "Alique, D."

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Continuous flowing electroless pore-plating to fabricate H2-Selective Pd-Membranes
(Elsevier, 2025-07-26) Santos-Carballés, A.J.; Vizcaíno, A.J.; Sanz, R.; Calles, J.A.; Alique, D.
This study presents a novel approach to fabricating hydrogen-selective palladium membranes by continuous flowing electroless pore-plating, hereafter referred to as cf-ELP-PP. This procedure aims to significantly advance the manufacturing processes of dense membranes. In fact, the transition from traditional batch to continuous methods enhances production efficiency and membrane quality, thus being possible to reach improved hydrogen permeation capabilities. Particularly, these novel membranes exhibited a H2-permeance ranging between 3.29⋅10􀀀 4 and 4.77⋅10􀀀 4 mol m􀀀 2 s􀀀 1 Pa􀀀 0.5 with H2/N2 ideal separation factor greater than 10,000 for the entire set of experiments. This research also addresses key challenges related to the stability and efficiency of membranes, providing relevant insights for their operation during prolonged times even if unfavorable operating conditions are adopted. All these findings underscore the potential of cf-ELP-PP membranes for effective hydrogen purification in a wide variety of future industrial applications, aligning with the increasing demand for sustainable energy solutions. Moreover, the work also paves future enhancements in hydrogen production and separation processes by providing valuable insights for researchers in fields of materials science, chemical engineering, and renewable energy technologies.
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.
Environmental and cost assessments criteria for selection of promising palladium membranes fabrication strategies
(Elsevier, 2023) Alique, D.; Leo, P.; Martinez-Diaz, D.; Calles, J.A.; Sanz, R.
Different strategies to prepare H2-selective composite-membranes demonstrate promising performances, although the selection of the optimum alternative must consider environmental and economic concerns. These aspects, scarce in the available literature, are addressed here to analyze the convenience of using diverse CeO2-based intermediate layers in composite Pd-membranes and recommend a maximum membrane length for scaling-up. The replacement of raw dense-CeO2 by porous or Pd-doped particles in the intermediate layer clearly improves the membrane performance, saving around 50% of required Pd-thickness while increasing the H2-permeance. However, porous-CeO2 almost doubles the major environmental impacts and support modification costs, overcoming the potential saving costs in palladium. On the contrary, dense Pd-doped CeO2 mitigates the environmental impacts by 27% and simultaneously saves 24% of expenses. Further reductions in environmental impacts and costs were reached after increasing the membrane-length up to 25 cm, becoming further improvements almost negligible for longer membranes.
Green hydrogen production by brewery spent grain valorization through gasification and membrane separation towards fuel-cell grade purity
(Elsevier, 2025-06-27) Alique, D.; Molina, G.; Maroño, M.; Santos-Carballés, A.J.; Sánchez-Hervás, J.M.; Ortíz, I.; Sanz, R.; Calles, J.A.; Martínez-Miguélez, A.; Navarro, C.
This study focuses on the potential valorization of brewers' spent grain (BSG) through gasification for ultra-pure green hydrogen production via membrane separation. First, a fundamental physicochemical characterization of BSG samples from two different Spanish brewing industries was conducted, revealing high energy content and good reproducibility of elemental composition, thus providing great potential for hydrogen generation in the context of circular economy for the brewery industry. The syngas composition reached by BSG gasification has been predicted and main operating conditions optimized to maximize the hydrogen yield (25–75 vol% air-steam mixture ratio, GR = 0.75, T = 800 °C and P = 5 bar). For gas purification, two Pd-membranes were fabricated by ELP-PP onto tubular PSS supports with high reproducibility (Pd-thickness in the range 8.22–8.75 μm), exhibiting an almost complete H2-selectivity, good fitting to Sieverts’ law and hydrogen permeate fluxes ranging from 175 to 550 mol m−2 h−1 under ideal gas feed composition conditions. The mechanical resistance of membranes was maintained at pressure driving forces up to 10 bar, thus highlighting their potential for commercialization and industrial application. Furthermore, long-term stability tests up to 75 h indicated promising membrane performance for continuous operation, offering valuable insights for stakeholders in the brewery industry to enhance economic growth and environmental sustainability through green hydrogen production from BSG.
High-Purity Green Hydrogen Production by Bio-oil/Ethanol Mixtures Steam Reforming in Pd-Based Membrane Reactors
(AIDIC, The Italian Association of Chemical Engineering, 2023-06-30) Iglesias-Vázquez, S.; Valecillos, J.; Remiro, A.; Landa, L.; Alique, D.; Santos-Carballes, A.J.; Sanz, R.; Calles, J.A.; Bilbao, J.; Gayubo, A.G.
The use of a membrane reactor (MR) for the reforming of biomass derived oxygenates is a promising approach to produce pure hydrogen from renewable sources. In this study, a Pd membrane supported on a porous stainless-steel (PSS) tube was fabricated by Electroless Pore Plating (ELP- PP) and tested in the steam reforming (SR) of bio-oil stabilized with 25 wt.% ethanol. All reaction tests were conducted in a reaction setup with two consecutive steps: (i) the thermal treatment for the vaporization of the bio-oil/ethanol mixture and the controlled deposition of pyrolytic lignin, and (ii) the SR reaction in an upwards-flow bed reactor with a Ni-based catalyst obtained upon reduction of a NiAl2O4 spinel. The Pd membrane was allocated in the middle of the SR reactor for its use as a MR. The reaction conditions were maintained at 580 °C with steam/carbon ratio of 2.5, space time of 0.15 h, feed pressure in the range of 1-3.3 bar, 0.1 bar in the permeate side, and time on stream of 4 h. The results reveal the enhancement of the hydrogen yield when using the MR at 3.3 bar and with the lowest gas velocity, allowing a hydrogen recovery of 57.74% with 99.8% purity. Consequently, the total hydrogen production in the MR operating at 3.3 bar and 0.6 cm s-1 increased from 0.309 to 0.367 g H2 (g C)-1 if compared to the conventional reactor at 1 bar and 0.9 cm·s-1.
Life cycle assessment of H2-selective Pd membranes fabricated by electroless pore-plating
(Elsevier, 2021) Martinez-Diaz, D.; Leo, P.; Sanz, R.; Carrero, A.; Calles, J.A.; Alique, D.
Pd-based membranes are attracting great attention to reach ultra-pure hydrogen in independent separators or combined with catalysts in membrane reactors. Many advances have been proposed for their fabrication over the last few years, reaching relatively thin Pd-films onto porous substrates with high permeation capacities and mechanical stability, although their commercialization and penetration in the industry are still scarce. At this point, it is important to complete all these technological advances with data about related economic and environmental implications during their fabrication to detect possible bottlenecks and select the best strategy. In this context, the current study presents for the first time a life cycle assessment focused on the preparation of Pd-based composite-membranes by Electroless Pore-Plating (ELP-PP). Two different types of composite membranes supported onto porous stainless steel tubes are analyzed, including or not an additional CeO2 intermediate layer between the support and the Pd-film. Precise experimental data of the fabrication process at laboratory-scale were considered to account for both materials and energy requirements. Thereafter, the environmental impacts were estimated through ReCiPe methodology by using the software Simapro 8.5. The results evidence that climate change (CC), human toxicity (HT), acidification (AC), freshwater ecotoxicity (FWE), metal depletion (MD) and fossil fuel resources depletion (FD) are the most relevant environmental impacts generated during the manufacturing of the Pd-based membrane. Under this perspective, palladium deposition appears as the manufacturing step with the highest impacts. It can be explained by the metal consumption and the high-energy consumption required for deposition cycles. Thus, the electricity mix of the country where the factory is located is critical to minimize the environmental impacts. For this reason, European countries are expected to be the most favorable ones for membrane fabrication. Finally, comparing both membrane types (with or without a CeO2 intermediate layer), it can be stated that the incorporation of the ceramic layer noticeably reduces the necessary amount of Pd to reach a fully dense membrane and therefore the associated environmental impacts.
New synthesis method of Pd membranes over tubular PSS supports via "pore-plating" for hydrogen separation processes
(Elsevier, 2012) Sanz, R.; Calles, J.A.; Alique, D.; Furones, L.
A new synthesis method to prepare Pd membranes by novelty modified electroless plating over tubular porous stainless steel supports (PSS) has been developed. This new pore plating method basically consists on feeding both plating solution and reducing agent from opposite sides of support, allowing the preparation of totally hydrogen selective membranes with a significantly lower Pd consumption than the corresponding to the conventional electroless plating procedure. In the latter, both reducing agent and plating solution are added simultaneously in one side of the PSS support. This new plating method has been applied over raw commercial PSS supports and air calcined supports in order to generate a Fe-Cr oxide intermediate layer. A completely dense Pd membrane with a thickness in the range 11-20 m directly over tubular porous stainless steel tubes with a high roughness has been achieved. The permeation properties of the membranes have been tested at different operating conditions for pure feed gases: retentate pressure (1 - 4 bar) and temperature (350 - 450ºC). All membranes present good permeance reproducibility after several thermal cycles and a complete hydrogen ideal selectivity, since complete retention of nitrogen is maintained for all tested experiment conditions, ensuring 100% purity in the hydrogen permeate flux. The permeance of both membranes is maintained in the range of 1-3 ·10-4 mol·m-2·s-1·Pa-0.5.
On the long-term stability of Pd-membranes with TiO2 intermediate layers for H2 purification
(Elsevier, 2021) Vizcaíno, J.A.; Alique, D.; Vizcaíno, A.J.; Calles, J.A.; Sanz, R.
This work addresses the use of TiO2-based particles as an intermediate layer for reaching fully dense Pd-membranes by Electroless Pore-Plating for long-time hydrogen separation. Two different intermediate layers formed by raw and Pd-doped TiO2 particles were considered. The estimated Pd-thickness of the composite membrane was reduced in half when the ceramic particles were doped with Pd nuclei before their incorporation onto the porous support by vacuum-assisted dip-coating. The real thickness of the top Pd-film was even lower (around 3 μm), as evidenced by the cross-section SEM images. However, a certain amount of palladium penetrates in some points of the porous structure of the support up to 50 μm in depth. In this manner, despite saving a noticeable amount of palladium during the membrane fabrication, lower H2-permeance was found while permeating pure hydrogen from the inner to the outer surface of the membrane at 400 °C (3.55·10−4 against 4.59·10−4 mol m−2 s−1 Pa−0.5). Certain concentration-polarization was found in the case of feeding binary H2–N2 mixtures for all the conditions, especially in the case of reaching the porous support before the Pd-film during the permeation process. Similarly, the effect of using sweep gas is more significant when applied on the side where the Pd-film is placed. Besides, both membranes showed good mechanical stability for around 200 h, obtaining a complete H2/N2 ideal separation factor for the entire set of experiments. At this point, this value decreased up to around 400 for the membrane prepared with raw TiO2 particles as intermediate layer (TiO2/Pd). At the same time, complete selectivity was maintained up to 1000 h in case of using doped TiO2 particles (Pd–TiO2/Pd). However, a specific decrease in the H2-permeate flux was found while operating at 450 °C due to a possible alloy between palladium and titanium that is not formed at a lower temperature (400 °C). Therefore, Pd–TiO2/Pd membranes prepared by Electroless Pore-Plating could be very attractive to be used under stable operation in either independent separators or membrane reactors in which moderate temperatures are required.
Preparation, testing and modelling of a hydrogen selective Pd/YSZ/SS composite membrane
(Elsevier, 2012) Sanz, R.; Calles, J.A.; Alique, D.; Furones, L.; Ordóñez, S.; Marín, P.; Corengia, P.; Fernández, E.
A palladium selective tubular membrane has been prepared to separate and purify hydrogen. The membrane consists of a composite material, formed by different layers: a stainless steel support (thickness of 1.9 mm), an yttria-stabilized zirconia interphase (thickness of 50 m) prepared by Atmospheric Plasma Spraying and a palladium layer (thickness of 27.7 m) prepared by Electroless Plating. The permeation properties of the membrane have been tested at different operating conditions: retentate pressure (1 - 5 bar), temperature (350 - 450ºC) and hydrogen molar fraction of feed gas (0.7 - 1). At 400ºC, a permeability of 1.1 · 10-8 mol/(s m Pa0.5) and a complete selectivity to hydrogen were obtained. The complete retention of nitrogen was maintained for all tested experiment conditions, with both single and mixtures of gases, ensuring 100% purity in the hydrogen permeate flux. A rigorous model considering all the resistances involved in the hydrogen transport has been applied for evaluating the relative importance of the different resistances, concluding that the transport through the palladium layer is the controlling one. In the same way, a model considering the axial variations of hydrogen concentration because of the cylindrical geometry of the experimental device has been applied to the fitting of the experimental data. The best fitting results have been obtained considering Sieverts¿-law dependences of the permeation on the hydrogen partial pressure.
Steam reforming of bio-oil stabilized with ethanol over a Ni/MgAl2O4 catalyst in a Pd-membrane reactor
(Elsevier, 2025-07-07) Iglesias-Vázquez, S.; Valecillos, J.; Remiro, Aingeru; Elordi, Gorka; Alique, D.; Santos-Carballes, A.J.; Sanz, R.; Calles, J.A.; Bilbao, J.; Gayubo, A.G.
A new membrane reactor (MR) has been used in the steam reforming (SR) of a feed of raw bio-oil stabilized with 25 wt% ethanol over a Ni/MgAl2O4 catalyst, comparing the results (yield of H2 and byproduct gases) to those reached in a conventional reactor (CR). The reaction setup involves two steps in series: a down-flow tube (at 500 ºC) for the vaporization of the feed and controlled removal of pyrolytic lignin (PL) from the oxygenates in the biooil, followed by an up-flow reactor provided with a composite Pd membrane supported on a porous stainless steel (PSS) tube containing a CeO2 intermediate layer (Pd/CeO2/PSS). In the MR configuration (with permeate pressure of 0.2 bar absolute), a H2 yield of 82 % was achieved at 550 ºC, space time of 2.8 h, S/C ratio of 1.55 and 3 bar in the retentate (reactor). This result significantly improves those reached in CR, even at 1 bar and 600 ºC. The S/C ratio in the feed must be limited in the MR configuration to avoid restrictions in H2 flux through the Pdmembrane caused by a higher gas dilution and concentration-polarization effect, as observed when the S/C ratio is increased up to 2.2. Similarly, a higher retentate pressure has a negative effect on the H2 yield due to its negative impact on the equilibrium of methane SR, that overcomes its benefits on the H2 permeation through the membrane. A promising performance of the membrane and catalyst has been obtained, thus demonstrating good prospects for their use in the sustainable production of H2 from lignocellulosic biomass