Examinando por Autor "Sanz, R."

Mostrando 1 - 10 de 10

CO2 adsorption on amine-functionalized clays
(Elsevier B.V., 2019) Gómez-Pozuelo, G.; Sanz-Pérez, E.S.; Arencibia, A.; Pizarro, P.; Sanz, R.; Serrano, D.P.
Carbon capture using amine-modified porous sorbents is one of the main proposed technologies to reduce the CO2 atmospheric concentration. In this work, a wide series of inexpensive clays have been selected to assess their role as supports of amine-containing sorbents for CO2 capture. Montmorillonite, bentonite, saponite, sepiolite and palygorskite have been hydrated and functionalized by three routes: (a) grafting with aminopropyl (AP) and diethylenetriamine (DT) organosilanes; (b) impregnation with polyethyleneimine (PEI); and (c) double functionalization by impregnating previously grafted samples. XRD, FTIR and N2 adsorption-desorption analyses along with nitrogen content and CO2 adsorption properties (thermogravimetry and fixed bed) have been evaluated for bare and functionalized clays. Under dry conditions (45 °C, 1 bar), grafted and impregnated samples yielded CO2 uptakes as high as 61.3 and 67.1 mg CO2/g ads (for Sepi-DT and Paly-PEI, respectively), with the latter being the best-performing sample in terms of CO2 uptake. On the contrary, double-functionalized samples displayed poor CO2 adsorption properties, probably due to pore-blocking problems related to their high organic loading. The presence of 5% H2O in the feed gas resulted in CO2 uptake increments from 17 to 27%. The adsorption performance of AP, DT and PEI-containing samples was maintained after three adsorption-desorption cycles
CO2 adsorption performance of aminofunctionalized SBA-15 under post-combustion conditions
(Elsevier, 2013) Sanz-Pérez, E.S.; Olivares-Marín, M.; Arencibia, A.; Sanz, R.; Calleja, G.; Maroto Valer, M.M.
Carbon dioxide adsorbents prepared from SBA-15 mesostructured silica functionalized with amino groups have been tested under a simulated gas mixture similar to that of a coal-fired thermal power plant. SBA-15 material was functionalized by grafting with aminopropyl-trimethoxysilane (AP (N)) and diethylene-triamine-trimethoxysilane (DT (NNN)), and by impregnation with polyethyleneimine (PEI) and tetraethylenepentamine (TEPA). CO2 adsorption performance was measured in both a thermobalance and in a fixed bed. A thorough study of the adsorption behaviour was carried out, including the influence of conditions found in real post-combustion operation processes, such as diluted CO2 concentration, presence of SO2 and moisture in the flue gas. The reutilization of the adsorbent by successive adsorption-desorption experiments has also been tested. Grafted materials and samples impregnated with around 50 % organic amount or higher, showed a small influence of the dilution of CO2 in the feed gas on their CO2 uptake. Adsorption capacity after 10 cycles remains almost unaltered for grafted and PEIimpregnated solids and moderately decreases for TEPA-impregnated adsorbent. CO2 adsorption capacity decreased significantly with the presence of 1,000 ppm SO2 for up to 5 cycles, finding a direct correlation with the nitrogen content of the sorbents. Humid conditions (5 % moisture) do not significantly affect adsorption capacity of grafted samples, but improve the CO2 uptake of impregnated adsorbents about 50-60 %, obtaining an adsorption capacity of 16.2 wt. % CO2 (3.7 mmol CO2/g) for sample SBA-TEPA (50) in a humid diluted CO2 stream (15 % CO2) at 45 ºC and 1 bar.
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.
Effect of the dual incorporation of fullerene and polyethyleneimine moieties into SBA-15 materials as platforms for drug delivery
(Springer Nature, 2019-05-28) Martín, A.; Morales, V.; Ortiz-Bustos, J.; Sanz, R.; García-Muñoz, R.A.
Mesostructured SBA-15 silica materials have been successfully dual functionalized with polyethyleneimine (PEI) groups and C60 fullerene moieties to allow an evaluation of their properties as nanovehicles for controlled drug delivery. Methylprednisolone sodium succinate was selected as a model drug for adsorption on the surface of functionalized SBA-15 silica materials. The resulting dual-functionalized SBA-15 silica materials exhibit mesoscopic arrangements, although with a remarkable reduction in their textural properties as compared to pure silica SBA-15. The adsorption capacity of methylprednisolone on functionalized SBA-15-PEI improved remarkably compared with that of raw SBA-15, while the drug release rate slowed, as the amount of PEI anchored in the SBA-15 increased. The strong attractive electrostatic interactions between methylprednisolone and the silica surfaces of SBA-15-PEI materials, measured by zeta potential, account for these results. In a second step, wherein C60 fullerene species in combination with PEI were grafted to the silica, the results establish that the steric effects and hydrophobicity of the C60 moieties hinder methylprednisolone transport within the silica pores. The kinetic parameters obtained from the drug release profiles, fitted to four kinetic models, show that the incorporation of C60 species yields lower methylprednisolone release rates from SBA-15-PEI-C60 materials than from SBA-15-PEI materials. Additionally, the incorporation of fullerene groups into PEI-modified materials provides an increment in cell viability. Confocal microscopy evidences the cellular internalization of the dual-functionalized mesoporous SBA-15 materials inside the plasmatic membrane.
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.
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.
Tailoring the properties of hierarchical TS-1 zeolite synthesized from silanized protozeolitic units
(2012) Serrano, D. P.; Sanz, R.; Pizarro, P.; Moreno, I.; ELSEVIER
Hierarchical TS-1 zeolites, characterized by having a secondary porosity within the supermicro/mesopore region (1.5-6 nm), have been synthesized following a procedure based on the silanization of protozeolitic units, which are previously generated by means of a precrystallization step. The silanization agent, phenylaminopropyltrimethoxysilane (PHAPTMS) acts as crystal growth inhibitor, hindering partially the protozeolitic units growth and aggregation during the crystallization treatment. Both the duration of the precrystallization step and the proportion of the organosilane compound added to the synthesis gel have a significant influence on the physicochemical and textural properties of the resultant materials. Thus, the best precrystallization time, leading to the most enhanced textural properties, is comprised between 22-24 hours. Using this time an appropriate balance between the number of protozeolitic units formed and their size is reached. On the other hand, by controlling the organosilane compound proportion added to synthesis gel, the contribution of the secondary porosity can be tailored. Likewise, amounts of organosilane larger than 5 mol% provide to a secondary porous system more uniform in size. The catalytic activity of these materials was evaluated in 1-octene and cyclohexene epoxidation reactions, using tert-butylhydroperoxide (TBHP) as oxidant. The olefin conversion and TOF values reached by hierarchical TS-1 zeolites are remarkably superior to that obtained with the conventional microporous TS-1 zeolite, being higher when the modification degree of the textural properties is more pronounced. These results can be ascribed to the higher accessibility of both TBHP and olefin to the titanium active sites located in the secondary porous system. Likewise, these zeolites exhibit a high oxidant efficiency and total selectivity to epoxide, parameters which are not affected by the presence of the secondary porosity.