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  • UV to far-IR reflectance spectra of carbonaceous chondrites - I. Implications for remote characterization of dark primitive asteroids targeted by sample-return missions

     Trigo-Rodríguez, José María; Moyano Cambero, Carles E.; Llorca Pique, Jordi; Fornasier, Sonia; Barucci, Maria Antonietta; Belskaya, Irina N.; Martins, Zita; Rivkin, Andrew S.; Dotto, Elisabetta; Madiedo, José María; Alonso Azcárate, Jacinto
    Monthly notices of the Royal Astronomical Society
    Date of publication: 2014-01-01
    Journal article

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    We analyse here a wide sample of carbonaceous chondrites from historic falls (e.g. Allende, Cold Bokkeveld, Kainsaz, Leoville, Murchison, Murray, Orgueil and Tagish Lake) and from NASA Antarctic collection.With the analysis of these meteorites we want to get new clues on the role of aqueous alteration in promoting the reflectance spectra diversity evidenced in the most primitive chondrite groups. The selected meteorite specimens are a sample large enough to exemplify how laboratory reflectance spectra of rare groups of carbonaceous chondrites exhibit distinctive features that can be used to remotely characterize the spectra of primitive asteroids. Our spectra cover the full electromagnetic spectrum from 0.2 to 25 µm by using two spectrometers. First one is an ultraviolet (UV)-near-infrared (NIR) spectrometer that covers the 0.2-2 µm window, while the second one is an attenuated total reflectance infrared spectrometer covering the 2-25 µm window. In particular, laboratory analyses in the UV-NIR window allow obtaining absolute reflectance by using standardized measurement procedures. We obtained reflectance spectra of specimens belonging to the CI, CM, CV, CR, CO, CK, CH, R and CB groups of carbonaceous chondrites plus some ungrouped ones, and it allows identifying characteristic features and bands for each class, plus getting clues on the influence of parent body aqueous alteration. These laboratory spectra can be compared with the remote spectra of asteroids, but the effects of terrestrial alteration forming (oxy)hydroxides need to be considered. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

    We analyse here a wide sample of carbonaceous chondrites from historic falls (e.g. Allende, Cold Bokkeveld, Kainsaz, Leoville, Murchison, Murray, Orgueil and Tagish Lake) and from NASA Antarctic collection.With the analysis of these meteorites we want to get new clues on the role of aqueous alteration in promoting the reflectance spectra diversity evidenced in the most primitive chondrite groups. The selected meteorite specimens are a sample large enough to exemplify how laboratory reflectance spectra of rare groups of carbonaceous chondrites exhibit distinctive features that can be used to remotely characterize the spectra of primitive asteroids. Our spectra cover the full electromagnetic spectrum from 0.2 to 25 μm by using two spectrometers. First one is an ultraviolet (UV)–near-infrared (NIR) spectrometer that covers the 0.2–2 μm window, while the second one is an attenuated total reflectance infrared spectrometer covering the 2–25 μm window. In particular, laboratory analyses in the UV–NIR window allow obtaining absolute reflectance by using standardized measurement procedures. We obtained reflectance spectra of specimens belonging to the CI, CM, CV, CR, CO, CK, CH, R and CB groups of carbonaceous chondrites plus some ungrouped ones, and it allows identifying characteristic features and bands for each class, plus getting clues on the influence of parent body aqueous alteration. These laboratory spectra can be compared with the remote spectra of asteroids, but the effects of terrestrial alteration forming (oxy)hydroxides need to be considered.

  • Conversion of glycerol over 10%Ni/y-Al2O3 catalyst

     Miranda Morales, Bárbara C.; Chimentao, Ricardo J; Santos, Jeannette B O; Gispert Guirado, Francesc; Llorca Pique, Jordi; Medina Cabello, Francisco; Lopez Bonillo, Francisco; Sueiras, Jesus Eduardo
    Applied catalysis B. Environmental
    Date of publication: 2014-04-05
    Journal article

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    The conversion of glycerol in gas phase and atmospheric pressure has been investigated over 10wt.% Ni/¿-Al2O3 catalyst. The catalysts were prepared with nickel nitrate and pre-treated with hydrogen in the range of 623-1073K. The resultant catalysts were characterized by N2-physisoption, H2-chemisorption, X-ray diffraction (XRD), TGA-MS, TEM, RAMAN, NH3-TPD, XPS, TPO-MS and XANES. The stability and the catalytic behavior of the catalysts were affected by the reduction pre-treatment. Glycerol reaction pathways were proposed based on dehydration, dehydrogenation and hydrogenolysis steps. The main products identified were: hydroxyacetone, pyruvaldehyde, pyruvic acid, lactic acid, lactide, acetaldehyde and methane. The number of exposed Ni atoms and the degree of reduction of the NiO species affected the hydrogenolysis reaction of glycerol to CH4 affecting the catalytic stability. The catalyst was deactivated by coke formation, by transformation of Ni phase to nickel carbide (Ni3C), as well as by oxidation of the Ni phase during the reaction. In addition, Raman analysis revealed two types of carbonaceous deposits over the used samples: on the Ni species and on the support. The regeneration treatment by oxidation-reduction reactivated the catalyst successfully. © 2013 Elsevier B.V.

    The conversion of glycerol in gas phase and atmospheric pressure has been investigated over 10 wt.% Ni/γ-Al2O3 catalyst. The catalysts were prepared with nickel nitrate and pre-treated with hydrogen in the range of 623–1073 K. The resultant catalysts were characterized by N2-physisoption, H2-chemisorption, X-ray diffraction (XRD), TGA-MS, TEM, RAMAN, NH3-TPD, XPS, TPO-MS and XANES. The stability and the catalytic behavior of the catalysts were affected by the reduction pre-treatment. Glycerol reaction pathways were proposed based on dehydration, dehydrogenation and hydrogenolysis steps. The main products identified were: hydroxyacetone, pyruvaldehyde, pyruvic acid, lactic acid, lactide, acetaldehyde and methane. The number of exposed Ni atoms and the degree of reduction of the NiO species affected the hydrogenolysis reaction of glycerol to CH4 affecting the catalytic stability. The catalyst was deactivated by coke formation, by transformation of Ni phase to nickel carbide (Ni3C), as well as by oxidation of the Ni phase during the reaction. In addition, Raman analysis revealed two types of carbonaceous deposits over the used samples: on the Ni species and on the support. The regeneration treatment by oxidation–reduction reactivated the catalyst successfully.

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    Experimental analysis of a degraded open-cathode PEM fuel cell stack  Open access

     Strahl, Stephan; Gasamans Rodríguez, Noemí; Llorca Pique, Jordi; Husar, Attila Peter
    International journal of hydrogen energy
    Date of publication: 2014
    Journal article

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    The well-known challenges to overcome in PEM fuel cell research are their relatively low durability and the high costs for the platinum catalysts. This work focuses on degradation mechanisms that are present in open-cathode PEM fuel cell systems and their links to the decaying fuel cell performance. Therefore a degraded, open-cathode, 20 cell, PEM fuel cell stack was analyzed by means of in-situ and ex-situ techniques. Voltage transients during external perturbations, such as changing temperature, humidity and stoichiometry show that degradation affects individual cells quite differently towards the end of life of the stack. Cells located close to the endplates of the stack show the biggest performance decay. Electrochemical impedance spectroscopy (EIS) data present non-reversible catalyst layer degradation but negligible membrane degradation of several cells. Post-mortem, ex-situ experiments, such as cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) show a significant active area loss of the first cells within the stack due to Pt dissolution, oxidation and agglomeration. Scanning electron microscope (SEM) images of the degraded cells in comparison with the normally working cells in the stack show severe carbon corrosion of the cathode catalyst layers.

    The well-known challenges to overcome in PEM fuel cell research are their relatively low durability and the high costs for the platinum catalysts. This work focuses on degradation mechanisms that are present in open-cathode PEM fuel cell systems and their links to the decaying fuel cell performance. Therefore a degraded, open-cathode, 20 cell, PEM fuel cell stack was analyzed by means of in-situ and ex-situ techniques. Voltage transients during external perturbations, such as changing temperature, humidity and stoichiometry show that degradation affects individual cells quite differently towards the end of life of the stack. Cells located close to the endplates of the stack show the biggest performance decay. Electrochemical impedance spectroscopy (EIS) data present non-reversible catalyst layer degradation but negligible membrane degradation of several cells. Post-mortem, ex-situ experiments, such as cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) show a significant active area loss of the first cells within the stack due to Pt dissolution, oxidation and agglomeration. Scanning electron microscope (SEM) images of the degraded cells in comparison with the normally working cells in the stack show severe carbon corrosion of the cathode catalyst layers.

  • Hydrogen photoproduction from bio-derived alcohols in an optical fiber honeycomb reactor loaded with Au/TiO2

     Taboada Cabellos, Elena; Angurell Purroy, Inmaculada; Llorca Pique, Jordi
    Journal of photochemistry and photobiology A. Chemistry
    Date of publication: 2014-05-01
    Journal article

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    Cordierite honeycombs loaded with 1 wt.% Au/TiO2 have been used in an optical fiber photoreactor illuminated with UV LEDs to produce hydrogen at 298 K from aqueous methanol, ethanol, glycerol, bio-ethanol, and bio-glycerol in liquid phase. The amount of alcohol has been varied between 1% and 100%. Under the same photoreaction conditions, the amount of hydrogen produced follows the trend: methanol similar to ethanol similar to glycerol > bio-ethanol >> bio-glycerol. Hydrogen photogeneration is significantly enhanced (4-5-fold increase) in the optical fiber honeycomb photoreactor with respect to a conventional slurry photoreactor. (C) 2014 Elsevier B.V. All rights reserved.

  • Effect of impregnation protocol in the metallic sites of Pt-Ag/activated carbon catalysts for water denitration

     Aristizabal, A.; Contreras, Sandra; Jimenez Divins, Nuria; Llorca Pique, Jordi; Medina Cabello, Francisco
    Applied surface science
    Date of publication: 2014-04-15
    Journal article

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    The influence of the Pt precursor and the impregnation protocol in the catalytic behavior of 3%Pt-1.5%Ag supported on activated carbon for water denitration in a continuous reactor was studied. Pt(NH3)(4)(NO3)(2) and H2PtCl6 were selected as Pt precursors. Five protocols were investigated: sequential impregnations (both sequences), co-impregnation, physical mixture of monometallic catalysts, and physical mixture of a bimetallic catalyst with a Pt monometallic catalyst. The samples were characterized by XRD, XPS, TPR, HRTEM and physisorption. It was found that the catalytic activity strongly depends on the synthesis protocol and the Pt precursor, which modify the particle size. Higher nitrate rates are achieved using H2PtCl6 than Pt(NH3)(4)(NO3)(2); this is mainly related to the smaller metal particle size of the former, evidenced by HRTEM. Nitrate consumption rate is directly related with the mean particle size. The physical mixture of monometallic catalysts resulted in the highest nitrogen rate. (C) 2014 Elsevier B.V. All rights reserved.

    The influence of the Pt precursor and the impregnation protocol in the catalytic behavior of 3%Pt-1.5%Ag supported on activated carbon for water denitration in a continuous reactor was studied. Pt(NH3)(4)(NO3)(2) and H2PtCl6 were selected as Pt precursors. Five protocols were investigated: sequential impregnations (both sequences), co-impregnation, physical mixture of monometallic catalysts, and physical mixture of a bimetallic catalyst with a Pt monometallic catalyst. The samples were characterized by XRD, XPS, TPR, HRTEM and physisorption. It was found that the catalytic activity strongly depends on the synthesis protocol and the Pt precursor, which modify the particle size. Higher nitrate rates are achieved using H2PtCl6 than Pt(NH3)(4)(NO3)(2); this is mainly related to the smaller metal particle size of the former, evidenced by HRTEM. Nitrate consumption rate is directly related with the mean particle size. The physical mixture of monometallic catalysts resulted in the highest nitrogen rate. (C) 2014 Elsevier B.V. All rights reserved.

  • Shape-dependent activity of ceria in soot combustion

     Aneggi, Eleonora; Wiater, Dawid; de Leitenburg, Carla; Llorca Pique, Jordi; Trovarelli, Alessandro
    ACS Catalysis
    Date of publication: 2014-01
    Journal article

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    In this study, a series of conventional polycrystalline ceria and single-crystalline ceria nanorods and nanocubes were prepared by hydrothermal methods, and their structural, redo; and morphological properties were investigated using XRD, SEM, HRTEM, BET, temperature-programmed reduction, and oxygen storage capacity measurements. According to HRTEM, they are characterized by exposure of different surfaces: {100} surface for nanocubes; {100}, {110}, and in part {111} for nanorods; and mainly {1 1 1} for conventional polycrystalline ceria, with a morphology dominated by {111}-enclosed octahedral particles. The presence of more-reactive exposed surfaces affects the reaction of soot oxidation positively, with an increase in activity in nanoshaped materials compared with conventional ceria. Thermal aging, although detrimental for surface area, is shown to affect morphology by promoting irregular truncation of edges and corners and development of more reactive surface combinations in all crystal shapes. It is likely that thermal treatment, starting from either cubes or octahedral particles, induces the formation of a similar particle geometry whose activity is dependent on the type of plane exposed and by the number an extension of edge and corners, thus linking reactivity of octahedral particles in conventional ceria powders with that of cubes in nanoshaped materials. The results indicate that soot oxidation is also a surface-dependent reaction, and catalyst design for this purpose should allow for surface structure morphology and its evolution against temperature.

    In this study, a series of conventional polycrystalline ceria and single-crystalline ceria nanorods and nanocubes were prepared by hydrothermal methods, and their structural, redo; and morphological properties were investigated using XRD, SEM, HRTEM, BET, temperature-programmed reduction, and oxygen storage capacity measurements. According to HRTEM, they are characterized by exposure of different surfaces: {100} surface for nanocubes; {100}, {110}, and in part {111} for nanorods; and mainly {1 1 1} for conventional polycrystalline ceria, with a morphology dominated by {111}-enclosed octahedral particles. The presence of more-reactive exposed surfaces affects the reaction of soot oxidation positively, with an increase in activity in nanoshaped materials compared with conventional ceria. Thermal aging, although detrimental for surface area, is shown to affect morphology by promoting irregular truncation of edges and corners and development of more reactive surface combinations in all crystal shapes. It is likely that thermal treatment, starting from either cubes or octahedral particles, induces the formation of a similar particle geometry whose activity is dependent on the type of plane exposed and by the number an extension of edge and corners, thus linking reactivity of octahedral particles in conventional ceria powders with that of cubes in nanoshaped materials. The results indicate that soot oxidation is also a surface-dependent reaction, and catalyst design for this purpose should allow for surface structure morphology and its evolution against temperature.

  • The formation of nanodomains of Ce6O11 in ceria catalyzed soot combustion

     Aneggi, Eleonora; Jimenez Divins, Nuria; de Leitenburg, Carla; Llorca Pique, Jordi; Trovarelli, Alessandro
    Journal of catalysis
    Date of publication: 2014-04
    Journal article

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    The behavior of a series of CeO2 catalysts in soot combustion reaction was investigated by HRTEM and XPS. It is shown that nanodomains of reduced ceria in the form of Ce6O11 develop during reaction under oxygen-containing atmosphere, supporting the idea that the reaction between CeO2 and carbon particulate results in the formation of a reduced ceria phase. The fact that oxygen-deficient cerium oxide particles are not in contact with soot, whereas regular CeO2 particles are also found in contact with particulate, may suggest that reaction with soot implies the extraction of oxygen from the CeO2 fluorite lattice, confirming the importance of redox mechanism in ceria-catalyzed soot oxidation.

    The behavior of a series of CeO2 catalysts in soot combustion reaction was investigated by HRTEM and XPS. It is shown that nanodomains of reduced ceria in the form of Ce6O11 develop during reaction under oxygen-containing atmosphere, supporting the idea that the reaction between CeO2 and carbon particulate results in the formation of a reduced ceria phase. The fact that oxygen-deficient cerium oxide particles are not in contact with soot, whereas regular CeO2 particles are also found in contact with particulate, may suggest that reaction with soot implies the extraction of oxygen from the CeO2 fluorite lattice, confirming the importance of redox mechanism in ceria-catalyzed soot oxidation.

  • The effect of ceria on the dynamics of CuO-Cu2O redox transformation: CuO-Cu2O hysteresis on ceria

     Colussi, Sara; Amoroso, Francesco; Katta, Lakshmi; Llorca Pique, Jordi; Trovarelli, Alessandro
    Catalysis letters
    Date of publication: 2014-06-01
    Journal article

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    CuO supported on ceria and alumina is prepared by incipient wetness impregnation and its redox behavior is investigated by means of XRD, XPS and TPO experiments. CuO on ZrO2 and on ceria-zirconia are also synthesized for comparison. The support plays a major role on the dynamics of CuO-Cu2O transformation. On Al2O3 the formation of CuAl2O4 inhibits any oxygen exchange during TPO experiments, while on ceria, zirconia and ceria-zirconia supported catalysts CuO decomposition and re-oxidation take place with a hysteresis similar to that observed for Pd-PdO transformation. On CeO2 the hysteresis is significantly reduced, indicating a strong effect of ceria on CuO-Cu2O redox cycle.

  • Dynamic photocatalytic hydrogen production from ethanol-water mixtures in an optical fiber honeycomb reactor loaded with Au/TiO2

     Taboada Cabellos, Elena; Angurell Purroy, Inmaculada; Llorca Pique, Jordi
    Journal of catalysis
    Date of publication: 2014-01-01
    Journal article

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    Cordierite honeycombs loaded with different amounts of Au/TiO2 have been used in an optical fiber photoreactor illuminated with UV LEDs to produce hydrogen from ethanol and water-ethanol mixtures. The photoreactions have been carried out at 298-348 K, volume hourly space velocities of 300-2100 h-1, Au contents of 0.5-2 wt.% with respect to TiO2, and ethanol molar contents of 1-100%. Excellent dispersion and homogeneous particle size of gold has been obtained by using pre-formed, dendrimer-encapsulated Au nanopartides. The best photocatalytic performance has been obtained over monoliths loaded with ca. 0.5 mg cm(-2) of Au/TiO2 (1.0-1.5 wt.% Au), which corresponds to a photocatalyst layer thickness of about 1 mu m. In gas phase, acetaldehyde adsorption onto the photocatalyst surface plays an important role in the dynamics of the photoprocess by affecting hydrogen evolution sites, which is improved with temperature and short contact times. Hydrogen photogeneration in liquid phase is significantly enhanced (fivefold increase) in the optical fiber honeycomb photoreactor with respect to a conventional slurry photoreactor. (C) 2013 Elsevier Inc. All rights reserved.

    Cordierite honeycombs loaded with different amounts of Au/TiO2 have been used in an optical fiber photoreactor illuminated with UV LEDs to produce hydrogen from ethanol and water-ethanol mixtures. The photoreactions have been carried out at 298-348 K, volume hourly space velocities of 300-2100 h-1, Au contents of 0.5-2 wt.% with respect to TiO2, and ethanol molar contents of 1-100%. Excellent dispersion and homogeneous particle size of gold has been obtained by using pre-formed, dendrimer-encapsulated Au nanopartides. The best photocatalytic performance has been obtained over monoliths loaded with ca. 0.5 mg cm(-2) of Au/TiO2 (1.0-1.5 wt.% Au), which corresponds to a photocatalyst layer thickness of about 1 mu m. In gas phase, acetaldehyde adsorption onto the photocatalyst surface plays an important role in the dynamics of the photoprocess by affecting hydrogen evolution sites, which is improved with temperature and short contact times. Hydrogen photogeneration in liquid phase is significantly enhanced (fivefold increase) in the optical fiber honeycomb photoreactor with respect to a conventional slurry photoreactor. (C) 2013 Elsevier Inc. All rights reserved.

  • Sulfonic acid-functionalized aerogels as high resistant to deactivation catalysts for the etherification of glycerol with isobutene

     González, Maria Dolores; Salagre, Pilar; Taboada Cabellos, Elena; Llorca Pique, Jordi; Molins, Elies; Cesteros, Yolanda
    Applied catalysis B. Environmental
    Date of publication: 2013-06-05
    Journal article

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    Silica aerogel and lyogel have been successfully sulfonated in one step by a simple post-synthesis method using microwaves as well as conventional heating. The use of microwaves allowed loading higher amounts of sulfonic acid groups in both silicas, according to the higher S/Si atomic ratio determined by XPS, and the higher sulfur content determined by TGA, also exhibiting lower surface area and higher acidity. Sulfonated aerogels showed higher conversion and selectivity to h-GTBE (glycerol di- and tri-ethers) than sulfonated lyogels for the acid-catalyzed etherification of glycerol with isobutene. This was attributed to the higher content of sulfonic acid groups incorporated in aerogel. Microwave-assisted sulfonated aerogel yielded 75% of selectivity to h-GTBE, which can be used as fuel additive, for practically total conversion. Interestingly, larger porosity of aerogel avoided the partial blocking of pores by reaction products observed when other micro- and mesoporous catalysts were tested for this reaction. The combination of high conversion, high selectivity to h-GTBE, practically no formation of undesired di-isobutylenes and very high resistance to catalyst deactivation makes microwave-assisted sulfonic acid functionalized aerogel a promising catalyst for this etherification reaction.

  • The Ksar Ghilane 002 shergottite-The 100th registered Martian meteorite fragment

     Llorca Pique, Jordi; Roszjar, Julia; Cartwright, Julia A.
    Meteoritic and Planetary Sciences
    Date of publication: 2013-03
    Journal article

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    We report on the discovery of a new shergottite from Tunisia, Ksar Ghilane (KG) 002. This single stone, weighing 538 g, is a coarse-grained basaltic shergottite, mainly composed of maskelynitized plagioclase (approximately 52 vol%) and pyroxene (approximately 37 vol%). It also contains Fe-rich olivine (approximately 4.5 vol%), large Ca-phosphates, including both merrillites and Cl-apatites (approximately 3.4 vol%), minor amounts of silica or SiO2-normative K-rich glass, pyrrhotite, Ti-magnetite, ilmenite, and accessory baddeleyite. The largest crystals of pyroxene and plagioclase reach sizes of approximately 4 to 5 mm. Pyroxenes (Fs26¿96En5¿50Wo2¿41). They typically range from cores of about Fs29En41Wo30 to rims of about Fs68En14Wo17. Maskelynite is Ab41¿49An39¿58Or1¿7 in composition, but some can be as anorthitic as An93. Olivine (Fa91¿96) occurs mainly within symplectitic intergrowths, in paragenesis with ilmenite, or at neighboring areas of symplectites. KG 002 is heavily shocked (S5) as indicated by mosaic extinction of pyroxenes, maskelynitized plagioclase, the occurrence of localized shock melt glass pockets, and low radiogenic He concentration. Oxygen isotopes confirm that it is a normal member of the SNC suite. KG 002 is slightly depleted in LREE and shows a positive Eu anomaly, providing evidence for complex magma genesis and mantle processes on Mars. Noble gases with a composition thought to be characteristic for Martian interior is a dominant component. Measurements of 10Be, 26Al, and 53Mn and comparison with Monte Carlo calculations of production rates indicate that KG 002 has been exposed to cosmic rays most likely as a single meteoroid body of 35¿65 cm radius. KG 002 strongly resembles Los Angeles and NWA 2800 basaltic shergottites in element composition, petrography, and mineral chemistry, suggesting a possible launch-pairing. The similar CRE ages of KG 002 and Los Angeles may suggest an ejection event at approximately 3.0 Ma.

    We report on the discovery of a new shergottite from Tunisia, Ksar Ghilane (KG) 002. This single stone, weighing 538 g, is a coarse-grained basaltic shergottite, mainly composed of maskelynitized plagioclase (approximately 52 vol%) and pyroxene (approximately 37 vol%). It also contains Fe-rich olivine (approximately 4.5 vol%), large Ca-phosphates, including both merrillites and Cl-apatites (approximately 3.4 vol%), minor amounts of silica or SiO2-normative K-rich glass, pyrrhotite, Ti-magnetite, ilmenite, and accessory baddeleyite. The largest crystals of pyroxene and plagioclase reach sizes of approximately 4 to 5 mm. Pyroxenes (Fs26–96En5–50Wo2–41). They typically range from cores of about Fs29En41Wo30 to rims of about Fs68En14Wo17. Maskelynite is Ab41–49An39–58Or1–7 in composition, but some can be as anorthitic as An93. Olivine (Fa91–96) occurs mainly within symplectitic intergrowths, in paragenesis with ilmenite, or at neighboring areas of symplectites. KG 002 is heavily shocked (S5) as indicated by mosaic extinction of pyroxenes, maskelynitized plagioclase, the occurrence of localized shock melt glass pockets, and low radiogenic He concentration. Oxygen isotopes confirm that it is a normal member of the SNC suite. KG 002 is slightly depleted in LREE and shows a positive Eu anomaly, providing evidence for complex magma genesis and mantle processes on Mars. Noble gases with a composition thought to be characteristic for Martian interior is a dominant component. Measurements of 10Be, 26Al, and 53Mn and comparison with Monte Carlo calculations of production rates indicate that KG 002 has been exposed to cosmic rays most likely as a single meteoroid body of 35–65 cm radius. KG 002 strongly resembles Los Angeles and NWA 2800 basaltic shergottites in element composition, petrography, and mineral chemistry, suggesting a possible launch-pairing. The similar CRE ages of KG 002 and Los Angeles may suggest an ejection event at approximately 3.0 Ma.

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    Hydrogen production by tuning the photonic band gap with the electronic band gap of TiO2  Open access

     Waterhouse, G.I.N; Wahab, A.K.; Al-Oufi, M.; Sun-Waterhouse, D.; Llorca Pique, Jordi; Idriss, H.
    Scientific reports
    Date of publication: 2013-10-10
    Journal article

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    Tuning the photonic band gap (PBG) to the electronic band gap (EBG) of Au/TiO2 catalysts resulted in considerable enhancement of the photocatalytic water splitting to hydrogen under direct sunlight. Au/TiO2 (PBG-357 nm) photocatalyst exhibited superior photocatalytic performance under both UV and sunlight compared to the Au/TiO2 (PBG-585 nm) photocatalyst and both are higher than Au/TiO2 without the 3 dimensionally ordered macro-porous structure materials. The very high photocatalytic activity is attributed to suppression of a fraction of electron-hole recombination route due to the co-incidence of the PBG with the EBG of TiO2 These materials that maintain their activity with very small amount of sacrificial agents (down to 0.5 vol.% of ethanol) are poised to find direct applications because of their high activity, low cost of the process, simplicity and stability.

    Tuning the photonic band gap (PBG) to the electronic band gap (EBG) of Au/TiO2 catalysts resulted in considerable enhancement of the photocatalytic water splitting to hydrogen under direct sunlight. Au/TiO2 (PBG-357 nm) photocatalyst exhibited superior photocatalytic performance under both UV and sunlight compared to the Au/TiO2 (PBG-585 nm) photocatalyst and both are higher than Au/TiO2 without the 3 dimensionally ordered macro-porous structure materials. The very high photocatalytic activity is attributed to suppression of a fraction of electron-hole recombination route due to the co-incidence of the PBG with the EBG of TiO2 These materials that maintain their activity with very small amount of sacrificial agents (down to 0.5 vol.% of ethanol) are poised to find direct applications because of their high activity, low cost of the process, simplicity and stability.

  • From Au(i) organometallic hydrogels to well-defined Au(0) nanoparticles

     Aguiló Linares, Elisabet; Gavara, Raquel; Lima, João Carlos; Llorca Pique, Jordi; Rodríguez Raurell, Laura
    Journal of materials chemistry C
    Date of publication: 2013-07-16
    Journal article

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    The reaction of water soluble phosphine 3,7-diacetyl-1,3,7-triaza-5- phosphabicyclo[3.3.1]nonane (DAPTA) with [Au(CC-C5H 4N)]n yields a luminescent water soluble phosphine gold(i) alkynyl complex [Au(4-pyridylethynyl)(DAPTA)] that leads to the formation of a luminescent hydrogel. A small variation of the phosphine structure (introduction of acetyl groups) with respect to the previously reported complex [Au(4-pyridylethynyl)(PTA)] has a clear effect on the observed properties: (i) a great increase in the hydrogel entanglement structure has been observed; (ii) the different cross-linking structures give rise to specific emission properties. The hydrogel was characterized by different techniques ( 1H-NMR, absorption and emission spectroscopy, optical microscopy, fluorescent microscopy (FM) and SEM). FM together with microspectrofluorimetry measurements has determined different emissive properties that vary according to the cross-linking process. Thermal treatments of the hydrogel produce well-defined metallic gold nanoparticles with a remarkable narrow size distribution, which have been characterized by SEM, TEM and X-ray photoelectron spectroscopy (XPS). At 200°C, Au particles measuring 1.0 ± 0.2 nm were obtained. Au nanoparticles were also formed as a result of electron beam irradiation

    The reaction of water soluble phosphine 3,7-diacetyl-1,3,7-triaza-5- phosphabicyclo[3.3.1]nonane (DAPTA) with [Au(CC-C5H 4N)]n yields a luminescent water soluble phosphine gold(i) alkynyl complex [Au(4-pyridylethynyl)(DAPTA)] that leads to the formation of a luminescent hydrogel. A small variation of the phosphine structure (introduction of acetyl groups) with respect to the previously reported complex [Au(4-pyridylethynyl)(PTA)] has a clear effect on the observed properties: (i) a great increase in the hydrogel entanglement structure has been observed; (ii) the different cross-linking structures give rise to specific emission properties. The hydrogel was characterized by different techniques ( 1H-NMR, absorption and emission spectroscopy, optical microscopy, fluorescent microscopy (FM) and SEM). FM together with microspectrofluorimetry measurements has determined different emissive properties that vary according to the cross-linking process. Thermal treatments of the hydrogel produce well-defined metallic gold nanoparticles with a remarkable narrow size distribution, which have been characterized by SEM, TEM and X-ray photoelectron spectroscopy (XPS). At 200°C, Au particles measuring 1.0 ± 0.2 nm were obtained. Au nanoparticles were also formed as a result of electron beam irradiation.

  • Purificación del aire mediante conjuntos estables de átomos de oro

     Santiago Redondo, Marta; Mendoza Gomez, Ernesto; Llorca Pique, Jordi
    Dyna
    Date of publication: 2013-06-04
    Journal article

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  • Ethanol steam reforming over hydrotalcite-derived Co catalysts doped with Pt and Rh

     Espinal, Raul; Taboada Cabellos, Elena; Molins, Elies; Chimentao, Ricardo J; Medina, Francisco; Llorca Pique, Jordi
    Topics in catalysis
    Date of publication: 2013-12
    Journal article

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    Honeycomb structures loaded with hydrotalcite-derived cobalt catalysts doped with various amounts of Pt and Rh have been tested in the steam reforming of ethanol at 523-823 K under different operational conditions. Catalysts promoted with noble metals are significantly more active than non-promoted hydrotalcite-derived cobalt but, at the same time, they build up carbon very efficiently. Electron microscopy, magnetic measurements and X-ray photoelectron spectroscopy reveal the occurrence of metal cobalt nanoparticles in the samples promoted with noble metals after reaction. According to the TPR profiles recorded over the hydrotalcite-derived cobalt catalysts doped with Pt and Rh, it is concluded that noble metals strongly promote cobalt reduction under ethanol steam reforming (ESR) conditions. Cobalt nanoparticles thus formed are very active for ethanol reforming but, at the same time, they originate severe carbon deposition. In contrast, non-promoted hydrotalcite-derived cobalt catalysts are less active for ESR but do not form carbon due to the absence of metallic cobalt.

    Honeycomb structures loaded with hydrotalcite-derived cobalt catalysts doped with various amounts of Pt and Rh have been tested in the steam reforming of ethanol at 523-823 K under different operational conditions. Catalysts promoted with noble metals are significantly more active than non-promoted hydrotalcite-derived cobalt but, at the same time, they build up carbon very efficiently. Electron microscopy, magnetic measurements and X-ray photoelectron spectroscopy reveal the occurrence of metal cobalt nanoparticles in the samples promoted with noble metals after reaction. According to the TPR profiles recorded over the hydrotalcite-derived cobalt catalysts doped with Pt and Rh, it is concluded that noble metals strongly promote cobalt reduction under ethanol steam reforming (ESR) conditions. Cobalt nanoparticles thus formed are very active for ethanol reforming but, at the same time, they originate severe carbon deposition. In contrast, non-promoted hydrotalcite-derived cobalt catalysts are less active for ESR but do not form carbon due to the absence of metallic cobalt.

  • Microwave-assisted synthesis of sulfonic acid-functionalized microporous materials for the catalytic etherification of glycerol with isobutene

     González, Maria Dolores; Salagre, Pilar; Taboada Ceballos, Elena; Llorca Pique, Jordi; Cesteros, Yolanda
    Greenchemistry
    Date of publication: 2013
    Journal article

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    Commercial Beta, ZSM-5 and mordenite zeolites and commercial montmorillonite K-10 were successfully sulfonated by a one-step simple method using microwaves. Different amounts of the sulfonating agent were required to maximize the incorporation of sulfonic groups for each structure. This has been related to the different dealumination degree suffered by the starting samples during sulfonation together with the different accessibility of the silanols to the sulfonic groups depending on the arrangement and size of their pores. All optimised sulfonated catalysts showed total conversion and very high selectivity (79¿91%) to h-GTBE (glycerol di- and tri-ethers), in spite of their microporosity, due to the incorporation of the sulfonic groups that led to a higher number and strength of Brønsted acid sites. Pore size and arrangement together with the external surface area of the catalysts affected the accessibility of the acid sites to the reactants, explaining the evolution of the catalytic results with time for each structure.

  • Bio-ethanol steam reforming and autothermal reforming in 3-m channels coated with RhPd/CeO2 for hydrogen generation

     Divins, N.J.; López, Eduardo; Rodriguez Martinez, Angel; Vega, Didac; Llorca Pique, Jordi
    Chemical engineering and processing
    Date of publication: 2013-02
    Journal article

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    A silicon micromonolith of 7 mm diameter and 0.2 mm length containing 1.5 million regular channels with a diameter of 3.3 µm was used for obtaining hydrogen through ethanol or bio-ethanol steam reforming (ESR) and oxidative steam reforming (OSR). The microchannels were coated with RhPd/CeO2 catalyst by a two-step method. First a CeO2 layer of ca. 100 nm thickness was deposited from cerium methoxyethoxide over a SiO2 layer, which was previously grown over the silicon microchannels by oxidation. Then, noble metals were grafted over the CeO2 support from chloride precursors. The unit was successfully tested for hydrogen production, achieving hydrogen rates of 180¿LH2¿cmR-3 for the steam reforming of bio-ethanol at 873 K, S/C = 2 and 0.009 s contact time. Reaction yields of 3.8 and 3.7 mol hydrogen generated per mol ethanol in feed were measured for ESR and OSR, respectively. A performance comparison was performed with a conventional cordierite monolith with the same catalyst formulation. Results show for the silicon microreactor an outstanding improvement of the specific hydrogen production rate, operating at considerably reduced residence times, due to the increase in contact area per unit volume.

    A silicon micromonolith of 7 mm diameter and 0.2 mm length containing 1.5 million regular channels with a diameter of 3.3 μm was used for obtaining hydrogen through ethanol or bio-ethanol steam reforming (ESR) and oxidative steam reforming (OSR). The microchannels were coated with RhPd/CeO2 catalyst by a two-step method. First a CeO2 layer of ca. 100 nm thickness was deposited from cerium methoxyethoxide over a SiO2 layer, which was previously grown over the silicon microchannels by oxidation. Then, noble metals were grafted over the CeO2 support from chloride precursors. The unit was successfully tested for hydrogen production, achieving hydrogen rates of 180 LH2 cmR−3 for the steam reforming of bio-ethanol at 873 K, S/C = 2 and 0.009 s contact time. Reaction yields of 3.8 and 3.7 mol hydrogen generated per mol ethanol in feed were measured for ESR and OSR, respectively. A performance comparison was performed with a conventional cordierite monolith with the same catalyst formulation. Results show for the silicon microreactor an outstanding improvement of the specific hydrogen production rate, operating at considerably reduced residence times, due to the increase in contact area per unit volume.

  • Synthesis and characterization of poly-l-leucine initialized and immobilized by rehydrated hydrotalcite: Understanding stability and the nature of interaction

     Miranda, Ronald Alexander; Finocchio, Elisabetta; Llorca Pique, Jordi; Medina, Francisco; Ramis, Gianguido; Sueiras, Jesus Eduardo; Segarra González, Anna Maria
    Physical chemistry chemical physics
    Date of publication: 2013-10-07
    Journal article

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    PLLs were synthesized by the ring-opening polycondensation (ROP) method using a-l-leucine N-carboxyanhydride (NCA) and initialized by triethylamine (Et3N), water or rehydrated hydrotalcite (HT rus). The role of temperature, different initiators and water in ROP was further investigated. In general, the initiators used in the polymerization reaction lead to PLL alpha-helical chains containing 5-40 monomers with NCA endgroups via a monomer-activated mechanism. However, the water has a twofold effect on ROP, as both a nucleophile and a base, which involves competition between two different types of initiating mechanisms (nucleophilic attack or deprotonation of the NCA monomer) in the polymerization reaction. This competition provides as a main product NCA endgroups with an alpha-helical structure and leads to the formation of the PLL cyclic-chains and beta-sheet structures which reduce the polymer Mw and the PD of the polypeptide. Furthermore, the water can hydrolyze the NCA endgroups resulting in PLL alpha-helical chains that contain living groups as the main product. On the other hand, the HTrus presents a double role: as both an initiator and a support. The polymers synthesized in the presence of HTrus presented a HT-carboxylate endgroup. The PLLs immobilized in HTrus through an anion-exchange method performed for just 30 minutes presented the PLL immobilized in the interlayer space of the HTrus. The PLL chains of the immobilized counterpart are stabilized by H-bonding with the M-OH of the HT structure. All the polypeptides and biohybrid materials synthesized have been characterized using different techniques (EA, ICP, XRD, Raman, MALDI-TOF, ESI-TOF, FT-IR at increasing temperatures, TG/DT analyses and TEM).

    PLLs were synthesized by the ring-opening polycondensation (ROP) method using α-L-leucine N-carboxyanhydride (NCA) and initialized by triethylamine (Et3N), water or rehydrated hydrotalcite (HTrus). The role of temperature, different initiators and water in ROP was further investigated. In general, the initiators used in the polymerization reaction lead to PLL alpha-helical chains containing 5–40 monomers with NCA endgroups via a monomer-activated mechanism. However, the water has a twofold effect on ROP, as both a nucleophile and a base, which involves competition between two different types of initiating mechanisms (nucleophilic attack or deprotonation of the NCA monomer) in the polymerization reaction. This competition provides as a main product NCA endgroups with an alpha-helical structure and leads to the formation of the PLL cyclic-chains and beta-sheet structures which reduce the polymer Mw and the PD of the polypeptide. Furthermore, the water can hydrolyze the NCA endgroups resulting in PLL alpha-helical chains that contain living groups as the main product. On the other hand, the HTrus presents a double role: as both an initiator and a support. The polymers synthesized in the presence of HTrus presented a HT-carboxylate endgroup. The PLLs immobilized in HTrus through an anion-exchange method performed for just 30 minutes presented the PLL immobilized in the interlayer space of the HTrus. The PLL chains of the immobilized counterpart are stabilized by H-bonding with the M–OH of the HT structure. All the polypeptides and biohybrid materials synthesized have been characterized using different techniques (EA, ICP, XRD, Raman, MALDI-TOF, ESI-TOF, FT-IR at increasing temperatures, TG/DT analyses and TEM).

  • Design of linear controllers applied to an ethanol steam reformer for PEM fuel cell applications

     García, Vanesa Mariel; Serra Prat, Maria; Llorca Pique, Jordi; Riera Colomer, Jordi
    International journal of hydrogen energy
    Date of publication: 2013
    Journal article

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    This paper focuses on the design of a controller for a low temperature ethanol steam reformer for the production of hydrogen to feed a Protonic Exchange Membrane (PEM) fuel cell. It describes different control structures for the reformer and treats the control structure selection of this Multiple Input Multiple Output (MIMO) system. For each control structure, decentralised 2x2 controllers with Proportional Integral (PI) control actions in each control loop are implemented. The PI parameters are tuned and the performance of the different linear controllers is compared through simulation. For the evaluation of the proposed controllers, the dynamic response for different initial conditions and changes in the references is analysed, as well as the behaviour of the controlled system against disturbances.

    This paper focuses on the design of a controller for a low temperature ethanol steam reformer for the production of hydrogen to feed a Protonic Exchange Membrane (PEM) fuel cell. It describes different control structures for the reformer and treats the control structure selection of this Multiple Input Multiple Output (MIMO) system. For each control structure, decentralised 2x2 controllers with Proportional Integral (PI) control actions in each control loop are implemented. The PI parameters are tuned and the performance of the different linear controllers is compared through simulation. For the evaluation of the proposed controllers, the dynamic response for different initial conditions and changes in the references is analysed, as well as the behaviour of the controlled system against disturbances.

    Postprint (author’s final draft)

  • Catalytic activity and characterization of Fe-Zn-Mg-Al hydrotalcites in biohydrogen production

     Wimonsong, Pornthip; Llorca Pique, Jordi; Nitisoravut, Rachnarin
    International journal of hydrogen energy
    Date of publication: 2013-08-21
    Journal article

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    Four different M2+-Mg-Al hydrotalcite (HT) materials were investigated for their effect on biohydrogen enhancement, where M2+ is Fe and/or Zn. HTs were synthesized by the coprecipitation method and characterized by infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD). The effect of Fe-Zn-Mg-Al HTs dose (0-833 mg/L) on hydrogen production was investigated in batch tests using sucrose-fed anaerobic mixed culture at 37 °C. The best catalytic activity was observed on Mg-Al HT at 167 mg/L with the maximum hydrogen yield of 2.30 ± 0.37 mol H2/mol sucrose, which was 44% higher than the control. The major metabolites detected in the test were acetic acid (3.6 g/L), butyric acid (4.1 g/L), and lactic acid (0.5 g/L). The basic properties of the different catalysts played an important role in stimulating or inhibiting the activity of hydrogen producing bacteria. Calcined Mg-Al HT did not promote biohydrogen production, suggesting that the catalytic enhancement was related to immobilization of bacteria in the electrostatically charged HT interlayers. Copyright © 2013, Hydrogen Energy Publications, LLC.

  • Room-temperature Suzuki-Miyaura reaction catalyzed by Pd supported on rare earth oxides: Influence of the point of zero charge on the catalytic activity

     Amoroso, Francesco; Colussi, Sara; del Zotto, Alessandro; Llorca Pique, Jordi; Trovarelli, Alessandro
    Catalysis letters
    Date of publication: 2013-06-01
    Journal article

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    Five Pd/REO (rare earth oxide) compounds (Pd/La2O3, Pd/CeO2, Pd/Pr6O11, Pd/Sm2O 3, and Pd/Gd2O3) have been successfully used as precatalysts in the Suzuki-Miyaura C-C cross-coupling reaction of aryl bromides with arylboronic acids in ethanol/water at r.t. All Pd/REO showed high activity and selectivity. The effective catalyst arises from palladium leaching from the REO support. We have demonstrated that the activity of each Pd/REO (the decreasing order is Pd/La2O3 > Pd/Pr6O 11 > Pd/Gd2O3 > Pd/Sm2O 3 » Pd/CeO2) is strictly related to the corresponding PZC (point of zero charge) value. Accordingly, it can be reasonably argued that the metal is released in solution in the form of Pd2+, and higher is the amount of positive charge on the surface in catalytic conditions, higher is the concentration of Pd2+ ions in solution and faster is the formation of the coupling product. Also the recycling of each Pd/REO is strictly connected with the PZC value of the REO support. As a matter of fact, Pd/CeO2, which has the lowest PZC value (6.7), shows the best reusability, according to its lower tendency to release Pd2+ ions in solution

    Five Pd/REO (rare earth oxide) compounds (Pd/La2O3, Pd/CeO2, Pd/Pr6O11, Pd/Sm2O 3, and Pd/Gd2O3) have been successfully used as precatalysts in the Suzuki-Miyaura C-C cross-coupling reaction of aryl bromides with arylboronic acids in ethanol/water at r.t. All Pd/REO showed high activity and selectivity. The effective catalyst arises from palladium leaching from the REO support. We have demonstrated that the activity of each Pd/REO (the decreasing order is Pd/La2O3 > Pd/Pr6O 11 > Pd/Gd2O3 > Pd/Sm2O 3 ≫ Pd/CeO2) is strictly related to the corresponding PZC (point of zero charge) value. Accordingly, it can be reasonably argued that the metal is released in solution in the form of Pd2+, and higher is the amount of positive charge on the surface in catalytic conditions, higher is the concentration of Pd2+ ions in solution and faster is the formation of the coupling product. Also the recycling of each Pd/REO is strictly connected with the PZC value of the REO support. As a matter of fact, Pd/CeO2, which has the lowest PZC value (6.7), shows the best reusability, according to its lower tendency to release Pd2+ ions in solution.

  • A general approach to fabricate fe3O4 nanoparticles decorated with Pd, Au, and Rh: Magnetically recoverable and reusable catalysts for Suzuki C-C cross-coupling reactions, hydrogenation, and sequential reactions

     Gonzàlez de Rivera, Ferran; Angurell Purroy, Inmaculada; Rossell Abrodos, Marta-Dacil; Erni, Rolf P.; Llorca Pique, Jordi; Jimenez Divins, Nuria; Müller Jevenois, Guillermo; Seco García, Miquel Angel; Rossell Alfonso, Josep Oriol
    Chemistry: a european journal
    Date of publication: 2013-09-02
    Journal article

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    A facile strategy has been explored for loading noble metals onto the surface of ferrite nanoparticles with the assistance of phosphine-functionalized linkers. Palladium loading is shown to occur with participation of both the phosphine function and the surface hydroxyl groups. Hybrid nanoparticles containing simultaneously Pd and Au (or Rh) are obtained by successive loading of metals. Similarly, ferrite nanoparticles decorated with Pd, Au, and Rh have also been formed by using the same strategy. The catalytic properties of the new nanoparticles are evidenced in processes such as reduction of 4-nitrophenol or hydrogenation of styrene. Besides, the sequential process involving a cross-coupling reaction followed by reduction of 1-nitrobiphenyl has been successfully achieved by employing Pd/Au decorated nanoferrite particles. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • Pd0.01Ru0.01Ce0.98O2-delta: A highly active and selective catalyst for the liquid phase hydrogenation of p-chloronitrobenzene under ambient conditions

     Mistri, Rajib; Llorca Pique, Jordi; Ray, Bidhan Chandra; Gayen, Arup
    Journal of molecular catalysis A. Chemical
    Date of publication: 2013-09
    Journal article

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    Nanostructured bimetal ion substituted ceria, Pd0.01Ru0.01Ce0.98O2-delta (PdRuC2), prepared for the first time by a novel solution combustion synthesis and characterized employing XRD, BET, HRTEM and XPS has been shown to be very active and selective than the monometal ion substituted analogue Pd0.02Ce0.98O2-delta (PdC2), whereas Ru0.02Ce0.98O2-delta (RuC2) is inactive towards liquid phase hydrogenation of p-chloronitrobenzene to p-chloroaniline under ambient conditions. Structural studies show metal ion substituted ceria as the predominant phase. The hydrogenation over PdRuC2 is completed beyond 75 min with 100% selectivity. Conversely, PdC2 hydrogenates similar to 40% of p-chloronitrobenzene with 82% selectivity. Increase of temperature from 35 degrees C to 80 degrees C showed a little higher activity of PdRuC2 but with a lower selectivity. The as-prepared and aged forms of PdRuC2 showed similar activity, whereas PdRuC2 heat-treated at 500 degrees C increased the conversion and the 800 degrees C heated catalyst reduced it (both similar to 2%) indicating high thermal stability. Maximum hydrogenation activity has been observed in ethanol as compared to methanol and butanol. The PdRuC2 catalyst also shows excellent hydrogenation activity towards o-, m-chloronitrobenzene and nitrobenzene. The enhancement of activity and selectivity of Pd in presence of Ru in the PdRu bimetal ionic catalyst for the hydrogenation reaction has been attributed to involvement of remarkable Ru4+-promotion in Pd0.01Ru0.01Ce0.98O2-delta.

    Nanostructured bimetal ion substituted ceria, Pd0.01Ru0.01Ce0.98O2−ı (PdRuC2), prepared for the first time by a novel solution combustion synthesis and characterized employing XRD, BET, HRTEM and XPS has been shown to be very active and selective than the monometal ion substituted analogue Pd0.02Ce0.98O2−ı (PdC2), whereas Ru0.02Ce0.98O2−ı (RuC2) is inactive towards liquid phase hydrogenation of p-chloronitrobenzene to p-chloroaniline under ambient conditions. Structural studies show metal ion substituted ceria as the predominant phase. The hydrogenation over PdRuC2 is completed beyond 75 min with 100% selectivity. Conversely, PdC2 hydrogenates ∼40% of p-chloronitrobenzene with 82% selectivity. Increase of temperature from 35 ◦C to 80 ◦C showed a little higher activity of PdRuC2 but with a lower selectivity. The as-prepared and aged forms of PdRuC2 showed similar activity, whereas PdRuC2 heat-treated at 500 ◦C increased the conversion and the 800 ◦C heated catalyst reduced it (both ∼2%) indicating high thermal stability. Maximum hydrogenation activity has been observed in ethanol as compared to methanol and butanol. The PdRuC2 catalyst also shows excellent hydrogenation activity towards o-, m-chloronitrobenzene and nitrobenzene. The enhancement of activity and selectivity of Pd in presence of Ru in the PdRu bimetal ionic catalyst for the hydrogenation reaction has been attributed to involvement of remarkable Ru4+-promotion in Pd0.01Ru0.01Ce0.98O2−ı.

  • Boosted CO2 reaction with methanol to yield dimethyl carbonate over Mg¿Al hydrotalcite-silica lyogels

     Stoian, Dragos Constantin; Taboada Ceballos, Elena; Llorca Pique, Jordi; Molins Grau, Elies; Medina Cabello, Francesc; Segarra González, Anna Maria
    Chemical communications
    Date of publication: 2013-05-13
    Journal article

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    Nonimmobilized and immobilized Mg¿Al hydrotalcite-like materials on silica lyogels were prepared and activated by calcination to be tested as catalysts in the direct carboxylation reaction of methanol. The HTs supportedon silica lyogels showedan important improvement andhigh stability in the direct synthesis reaction of DMC from CO2 and MeOH.

    Nonimmobilized and immobilized Mg–Al hydrotalcite-like materials on silica lyogels were prepared and activated by calcination to be tested as catalysts in the direct carboxylation reaction of methanol. The HTs supportedon silica lyogels showedan important improvement andhigh stability in the direct synthesis reaction of DMC from CO2 and MeOH.

  • A luminescent hydrogel based on a new Au(i) complex

     Gavara, Raquel; Llorca Pique, Jordi; Lima, Joao Carlos; Rodríguez Raurell, Laura
    Chemical communications
    Date of publication: 2013-01-04
    Journal article

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    The reaction of the water soluble phosphine 1,3,5-triaza-7-phosphaadamantane (PTA) with [Au(C[triple bond, length as m-dash]C¿C5H4N)]n yields the highly luminescent water soluble [(PTA)Au(4-pyridylethynyl)] complex. A detailed analysis of the compound shows the formation of gel structure giving rise to very long fibers, being the first example reported with such a simple structure.

    The reaction of the water soluble phosphine 1,3,5-triaza-7-phosphaadamantane (PTA) with [Au(CRC–C5H4N)]n yields the highly luminescent water soluble [(PTA)Au(4-pyridylethynyl)] complex. A detailed analysis of the compound shows the formation of gel structure giving rise to very long fibers, being the first example reported with such a simple structure.

  • PdCu alloy nanoparticles on alumina as selective catalysts for trichloroethylene hydrodechlorination to ethylene

     Meshesha, B.T.; Barrabes, Noelia; Llorca Pique, Jordi; Dafinov, Antonio; Medina, Francisco; Foettinger, Karin
    Applied catalysis A. General
    Date of publication: 2013-02-26
    Journal article

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    PdCu bimetallic catalysts supported on alumina were prepared by different common impregnation protocols and by a polyol nanoparticles synthesis route. These materials were studied in order to establish the relationship between structure, particle size, Pd–Cu interaction and catalytic activity/selectivity in the hydrodechlorination of trichloroethylene (TCE) in gas phase. The surface properties and the interaction between Cu and Pd in the bimetallic particles, as well as their catalytic behaviour are strongly influenced by the preparation protocol. Depending on the synthesis, PdCu alloy formation or isolated phases were observed. The presence of isolated Pd particles leads to high ethane selectivity, whereas upon alloy formation or strong interaction between Pd and Cu a higher ethylene yield was obtained. By the nanoparticles polyol synthesis, Pd-Cu alloy formation was obtained, leading to total selectivity to ethylene in the TCE hydrodechlorination reaction. On the Pd monometallic catalysts larger particle size resulted in higher levels of ethylene formation.

  • Ethanol catalytic membrane reformer for direct PEM FC feeding

     Koch, Reinhold; López, Eduardo; Riera Colomer, Jordi; Allué Fantova, Miguel; Jossen, Andreas; Jimenez Divins, Nuria; Llorca Pique, Jordi
    International journal of hydrogen energy
    Date of publication: 2013
    Journal article

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    In this paper an ethanol reformer based on catalytic steam reforming with a catalytic honeycomb loaded with RhPd/CeO2 and palladium separation membranes with an area of 30.4 cm2 has been used to generate a pure hydrogen stream of up to 100 ml/min to feed a PEM fuel cell with an active area of 5 cm2. The fuel reformer behavior has been extensively studied under different temperature, ethanol¿water flow rate and gas pressure at a fixed S/C ratio of 1.6 (molar). The hydrogen yield has been controlled by acting upon the ethanol¿water fuel flow and gas pressure. A mathematical model of the ethanol reformer has been developed and an adaptive and predictive control has been implemented on a real time system to take account of its nonlinear behavior. With this control the response time of the reformer can be reduced by a factor of 7 down to 8 s. The improved dynamics of the controlled reformer match better the quickly changing hydrogen demands of fuel cells. They reached a magnitude where costly hydrogen buffers between the reformer and the fuel cell can be omitted and an electric buffer at the output of the fuel cell is sufficient.

    In this paper an ethanol reformer based on catalytic steam reforming with a catalytic honeycomb loaded with RhPd/CeO2 and palladium separation membranes with an area of 30.4 cm2 has been used to generate a pure hydrogen stream of up to 100 ml/min to feed a PEM fuel cell with an active area of 5 cm2. The fuel reformer behavior has been extensively studied under different temperature, ethanol–water flow rate and gas pressure at a fixed S/C ratio of 1.6 (molar). The hydrogen yield has been controlled by acting upon the ethanol–water fuel flow and gas pressure. A mathematical model of the ethanol reformer has been developed and an adaptive and predictive control has been implemented on a real time system to take account of its nonlinear behavior. With this control the response time of the reformer can be reduced by a factor of 7 down to 8 s. The improved dynamics of the controlled reformer match better the quickly changing hydrogen demands of fuel cells. They reached a magnitude where costly hydrogen buffers between the reformer and the fuel cell can be omitted and an electric buffer at the output of the fuel cell is sufficient.

  • Hydrogen from bioethanol. Remewable yydrogen technologies. Chapter 7

     Llorca Pique, Jordi
    Date of publication: 2013-05-01
    Book chapter

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  • CuZn/ZrO2 catalytic honeycombs for dimethyl ether steam reforming and autothermal reforming

     Ledesma Rodriguez, Cristian; Llorca Pique, Jordi
    Fuel (Guildford)
    Date of publication: 2013-02
    Journal article

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    Dimethyl ether (DME) steam reforming simulating practical applications was tested over catalytic honeycombs coated with ZrO2 and loaded with different amounts of Cu and Zn. The best catalytic performance in terms of activity and yield towards the reforming products, H2 and CO2, was exhibited by CuZn/ ZrO2 with a Cu:Zn molar ratio of 1:10, which also showed high stability. SEM and XPS characterization showed that this catalyst contains very well-dispersed copper particles in contact with ZnO. Catalytic monoliths were also tested in the DME autothermal reforming reaction, but a strong deactivation was observed, probably due to the prevalence of methoxy species that lead to the formation of methane and carbon residues, as evidenced by in situ FTIR and XPS experiments.

    Dimethyl ether (DME) steam reforming simulating practical applications was tested over catalytic honeycombs coated with ZrO2 and loaded with different amounts of Cu and Zn. The best catalytic performance in terms of activity and yield towards the reforming products, H2 and CO2, was exhibited by CuZn/ ZrO2 with a Cu:Zn molar ratio of 1:10, which also showed high stability. SEM and XPS characterization showed that this catalyst contains very well-dispersed copper particles in contact with ZnO. Catalytic monoliths were also tested in the DME autothermal reforming reaction, but a strong deactivation was observed, probably due to the prevalence of methoxy species that lead to the formation of methane and carbon residues, as evidenced by in situ FTIR and XPS experiments

  • Q-00032

     Llorca Pique, Jordi
    Participation in a competitive project

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  • Hydrogen production from bioethanol using cobalt hydrotalcites.  Open access

     Espinal Bustos, Raúl Uziel
    Defense's date: 2013-12-20
    Universitat Politècnica de Catalunya
    Theses

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    El hidrógeno se perfila como un vector energético que puede ayudarnos a gestionar la energía de una manera más eficiente. El hidrógeno se puede almacenar y usar para producir electricidad en las pilas de combustible, en las que se combina con el oxígeno del aire y genera únicamente agua como subproducto. De las distintas maneras que existen para producir hidrógeno, la reacción catalítica entre el etanol y el agua (reformado) constituye una de las mejores opciones, ya que el etanol se produce fácilmente a partir de la biomasa (bioetanol) y es un substrato líquido y fácilmente manipulable. En esta tesis doctoral se ha estudiado el comportamiento de una familia de catalizadores de cobalto para llevar a cabo la producción de hidrógeno a partir de etanol y agua; concretamente, catalizadores basados en hidrotalcitas de cobalto. Existen otros catalizadores para llevar a cabo este mismo proceso, pero muchos de ellos tienen un coste elevado porque contienen metales nobles y otros se desactivan con facilidad por deposición de carbón en su superficie (los basados en níquel y cobalto). En esta tesis se demuestra que mediante un método preciso de preparación a partir de hidrotalcitas de cobalto se consiguen catalizadores de bajo coste y muy estables bajo condiciones reales de operación.El capítulo 1 es una introducción a los aspectos más destacables de la tesis doctoral, en el que se plantean los objetivos que se quieren abordar y se incluyen el estado del arte y los fundamentos en los que se basa el trabajo experimental realizado. Además de la naturaleza de los catalizadores y de las reacciones que se van a estudiar, en la introducción también se explica qué son y por qué se utilizan en esta tesis monolitos de cordierita como soportes físicos de los catalizadores y reactores catalíticos de membrana. Y es que esta tesis doctoral persigue, por un lado, la adquisición de nuevo conocimiento científico y, por otro lado, la aplicación de este conocimiento en el desarrollo de dispositivos útiles en aplicaciones reales.En los capítulos siguientes, la tesis doctoral constituye un compendio de artículos publicados en revistas internacionales de prestigio (3 artículos publicados y 1 artículo en proceso de revisión).En el capítulo 2 se describe la preparación de una familia de hidrotalcitas de cobalto con distinto contenido de cobalto, magnesio y aluminio y su comportamiento catalítico en la reacción de reformado de etanol con vapor para la producción de hidrógeno. A partir de una caracterización pormenorizada mediante distintas técnicas instrumentales, entre las que se incluyen la microscopía electrónica de barrido, microscopía electrónica de transmisión, difracción de rayos X, medidas de magnetismo a temperatura variable, espectroscopia infrarroja, análisis termogravimétricos, y experimentos in-situ con espectroscopía fotoelectrónica de rayos X, se identifican las especies químicas presentes y su estructura en los catalizadores antes, durante, y después de la reacción, poniéndose de manifiesto que la mejor formulación (la que ofrece un rendimiento a hidrógeno más elevado y sobre la que apenas se depositan residuos carbonosos) corresponde a una hidrotalcita con una relación Co:Mg:Al de 1:2:1. Asimismo se concluye que el catalizador preparado a partir de esta hidrotalcita se transforma a una mezcla de espinela de cobalto interaccionando fuertemente con MgO a escala nanométrica bajo las condiciones de reacción. Sin embargo, al realizar la reacción exclusivamente con la espinela de cobalto (preparada por separado a tal efecto) se obtiene una producción de hidrógeno menor, lo que demuestra que la hidrotalcita de cobalto usada como precursor del catalizador ejerce un control decisivo en la estructura del mismo. En el capítulo 3 se estudia la influencia del dopaje de la hidrotalcita Co:Mg:Al=1:2:1 con Pt y Rh. . Para ello se han preparado dos familias de catalizadores con distinto contenido de Pt y Rh.

    Hydrogen constitutes a promising alternative to manage our energy supply more efficiently. Hydrogen can be stored and used in fuel cells to produce electricity, where it combines with the oxygen present in the air and generates solely water as by-product. Of the different methods available to produce hydrogen, the catalytic reaction of ethanol and water (reforming) is one of the most advantageous alternatives, since ethanol can be produced easily from biomass (bioethanol), is liquid and simple to manipulate. This doctoral thesis studies the behavior of a family of cobalt catalysts to produce hydrogen from ethanol and water; to be more precise, catalysts based on cobalt hydrotalcites. The same process could be triggered by other types of catalyst, but many of them are far more expensive due to the noble metals they contain, and others - those based on nickel and cobalt - desactivate after a short amount of time because their surface accumulate carbon. This thesis demonstrates that with the help of a precise method of preparation, one can create inexpensive catalysts from cobalt hydrotalcites, which remain quite stable under realistic operating conditions. Chapter 1 introduces the reader to the key aspects of this doctoral thesis. It explains the objectives pursued and gives an overview of the state of art and the groundwork on which the experimental work is based. Besides explaining the general characteristics of the catalysts and the reactions that will be studied, chapter 1 also informs about cordierite monoliths: what exactly are they and why are they used in this work to physically stabilize the catalysts and catalytic membrane reactors. In this way, the aim of this doctoral thesis is to acquire new scientific knowledge on the one hand and on the other, to apply this knowledge in the development of devices that can be applied in practice. The four chapters following thereafter form a compound of papers that have been published in notable international journals (three of them) and one article in process of revision. Chapter 2 describes the preparation of a family of cobalt hydrotalcites with different ratios of cobalt, magnesia and aluminum, and how these cobalt hydrotalcites behave in the ethanol steam reforming reaction to produce hydrogen. Starting from a detailed characterization using different techniques like TEM, XRD, IR, TGA, In situ XPS, magnetism, etc., the different chemical elements present are identified, and their structure in the catalysts before, during, and after reaction is analyzed. It becomes evident that the best formula (with the greatest yield of hydrogen and the least amount of coke residual) is a hydrotalcite with a relation of Co:Mg:Al=1:2:1. It is concluded that during the reaction, the hydrotalcite-based catalyst transforms itself to a mix of cobalt spinel, strongly interacting with MgO on a nanometric scale. Nevertheless, if the reaction is repeated using only cobalt spinel (synthesized specifically for this purpose), the outcome is a smaller amount of hydrogen. This shows that cobalt hydrotalcite used as a catalyst precursor plays a crucial part in the final structure of the catalyst. Hydrotalcite Co:Mg:Al=1:2:1 doped with Pt and Rh is studied in chapter 3. For this, two families of catalysts with different ratios of Pt and Rh were prepared. They were analyzed under the same conditions as explained in chapter 2 and were tested in the reaction. The objective of doping the cobalt hydrotalcite with noble metals was to facilitate the reaction of cobalt, given the fact that metallic cobalt is the active element in ethanol steam reforming. Besides this key function of metallic cobalt, chapter 2 also reveals, however, that metallic cobalt speeds up the catalyst deactivation by causing severe coke accumulation. Hydrotalcite Co:Mg:Al=1:2:1 doped with Pt and Rh is studied in chapter 3. For this, two families of catalysts with different ratios of Pt and Rh were prepared.

  • Ethanol steam reforming for hydrogen generation over structured catalysts

     López, E; Jimenez Divins, Nuria; Anzola, Andrés; Schbib, Susana; Borio, Daniel O.; Llorca Pique, Jordi
    International journal of hydrogen energy
    Date of publication: 2013-04
    Journal article

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    The present paper reports on the preparation, characterization and reaction evaluation of structured catalysts toward hydrogen generation via ethanol steam reforming. To these ends, 400 cpsi cordierite monoliths were functionalized with RhePd/CeO2 catalyst. SEM, TEM and XRD showed a uniform and well-covering CeO2 layer where RhePd nanoparticles of less than 0.5 nm were anchored. The functionalized monoliths were successfully tested for synthesis gas production from ethanol steam reforming. Realistic operating conditions were selected, including temperatures between 500 and 950 K, pressures from 1 to 6 bar, undiluted ethanol:water molar ratios 1:4e1:8 (i.e., 2 S/C 4) and a wide range of feed loads. Appropriate activity and hydrogen selectivity were verified for the catalytic system, with ca. complete ethanol conversion at T > 700 K and a minor, or even negligible, generation of by-products (acetaldehyde, acetone, ethane, ethylene). Operating at 950 K and 1.5 bar, a H2 yield of 3.4 mol hydrogen per mol ethanol in feed was achieved for a liquid feed load of 0.22 mlliq/(mgcat min) (S/C ¼ 3), with 8.1% of CH4 and 8.2% of CO on dry basis. Kinetic parameters of a phenomenological set of reaction rate equations were fitted against experimental data, considering ethanol decomposition (methane formation) with subsequent methane steam reforming to both CO and CO2 and wateregas shift reaction. Copyright ª 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

  • Macroporous silicon microreactor for the preferential oxidation of CO

     Jimenez Divins, Nuria; López, E.; Llorca Pique, Jordi; Vega, Didac; Rodríguez, A.; Gonzàlez de Rivera, Ferran; Angurell Purroy, Inmaculada; Seco García, Miquel Angel; Rossell Alfonso, Josep Oriol
    IEEE Electron Devices (CDE)
    Date of publication: 2013
    Journal article

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    A macroporous silicon micromonolith containing ca. 40,000 regular channels of 3.3 ¿m in diameter per square millimeter has been successfully functionalized with an Au/TiO2 catalyst for CO preferential oxidation (CO-PrOx) in the presence of hydrogen. The functionalization of the silicon microchannels has been accomplished by growing a SiO2 layer on the channel walls, followed by exchange with a titanium alkoxyde precursor and decomposition into TiO2 and, finally, by anchoring carbosilanethiol dendron protected pre-formed Au nanoparticles. Catalytically active centers at the Au-TiO2 interface have been obtained by thermal activation. With this method, an excellent homogeneity and adherence of the catalytic layer over the microchannels of the macroporous silicon micromonolith has been obtained, which has been tested for CO-PrOx at 363-433 K and ¿=2 under H2/CO=0-20 (molar). The macroporous silicon micromonolith converts ca. 3 NmL of CO per minute and mL of microreactor at 433 K under H2/CO=20, suggesting that it could be particularly effective for hydrogen purification in lowtemperature microfuel cells for portable applications.

  • Gold nanoclusters for efficient removal of organic pollutants at room temperature

     Santiago Redondo, Marta; Blázquez Gómez, Zaira; Galindo, Edurne; Alves, Leonor; Llorca Pique, Jordi; Mendoza Gomez, Ernesto
    Submarine Air Monitoring and Air Purification
    Presentation's date: 2013-10-15
    Presentation of work at congresses

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    Preserving air quality of an enclosed space such as a submarine is a major challenge yet to be addressed. Currently, CO-H2 burners are employed to maintain a breathable air environment inside the submarine through catalytic conversion of contaminants being present in the air thereof into CO2 + H2O. These burners use a mixture of manganese and copper oxides referred to as hopcalite. Unfortunately, this catalyst presents a reasonable oxidation activity only above 150ºC as it suffers from strong inhibition by the presence of moisture. Furthermore, at such high operating temperatures, partial oxidation of hydrocarbons over the hopcalite may generate toxic by-products such as HF and HCl. Herein, we present a novel catalyst based on gold nanoclusters capable of eliminating massive amounts of organic pollutants at room temperature even in the presence of moisture.

    Preserving air quality of an enclosed space such as a submarine is a major challenge yet to be addressed. Currently, CO-H2 burners are employed to maintain a breathable air environment inside the submarine through catalytic conversion of contaminants being present in the air thereof into CO2 + H2O. These burners use a mixture of manganese and copper oxides referred to as hopcalite. Unfortunately, this catalyst presents a reasonable oxidation activity only above 150ºC as it suffers from strong inhibition by the presence of moisture. Furthermore, at such high operating temperatures, partial oxidation of hydrocarbons over the hopcalite may generate toxic by-products such as HF and HCl. Herein, we present a novel catalyst based on gold nanoclusters capable of eliminating massive amounts of organic pollutants at room temperature even in the presence of moisture.

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    Experimental analysis of a degraded open-cathode PEM fuel cell stack  Open access

     Strahl, Stephan; Gasamans Rodríguez, Noemí; Llorca Pique, Jordi; Husar, Attila Peter
    Iberian Symposium on Hydrogen Fuel Cells and Advanced Batteries
    Presentation's date: 2013
    Presentation of work at congresses

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    The well-known challenges to be overcome in PEM fuel cell research are their relatively low durability and high costs for the platinum catalysts. Thus, this work focuses on factors that impact durability and the links to the fuel cell performance. Therefore a degraded, open-cathode, 20-cell, PEM fuel cell stack, which was used in a laboratory test station for characterization experiments, was analyzed experimentally. Voltage transients during external perturbations, such as changing temperature, humidity and stoichiometries show that degradation affects individual cells quite differently throughout the lifetime of the stack. Electrochemical impedance spectroscopy (EIS) data presents non-reversible catalyst layer and membrane degradation of several cells. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) are in progress in order to validate the results of the electrical analysis and elucidate catalyst and membrane degradation.

  • Premi ICREA Acadèmia

     Masoller Alonso, Cristina; Garcia Ojalvo, Jorge; Llorca Pique, Jordi
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  • Ethanol photoreaction to hydrogen over Au/TiO(2) catalysts. Investigating the synergistic effect of nanoparticles

     Waterhouse, G.I.N; Murdoch, M.; Llorca Pique, Jordi; Idriss, Hicham
    International journal of nanotechnology
    Date of publication: 2012
    Journal article

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  • Pt-Cu bimetallic catalysts obtained from layered double hydroxides by an anion-exchange route

     Barrabes, Noelia; Frare, A.; Foettinger, Karin; Urakawa, A.; Llorca Pique, Jordi; Rupprechter, Guenther; Tichit, D.
    Applied clay science
    Date of publication: 2012-11
    Journal article

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  • Pt-Ag/activated carbon catalysts for water denitration in a continuous reactor: Incidence of the metal loading, Pt/Ag atomic ratio and Pt metal precursor

     Aristizabal, A.; Contreras, Sandra; Jimenez Divins, Nuria; Llorca Pique, Jordi; Medina, Francisco
    Applied catalysis B. Environmental
    Date of publication: 2012-10-30
    Journal article

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    Several Pt–Ag catalysts supported on activated carbon powder were tested in the catalytic reduction of nitrates in a continuous flow reactor. The influence of the noble metal precursor (Pt(NH3)4(NO3)2 or H2PtCl6), the Pt/Ag atomic ratio (0.3, 1.1 and 1.8) and the metal loading (3% or 1% Pt) were studied. The samples were characterized by XRD, TPR, HRTEM, XPS, H2-chemisorption and nitrogen physisorption. The results showed that the most important variables affecting the catalytic activity are the noble metal precursor and the metal loading, whereas the Pt/Ag atomic ratio does not affect significantly the catalytic behavior. The use of H2PtCl6 instead of Pt(NH3)4(NO3)2 as noble metal precursor leads to more active catalysts. The nitrate conversion is enhanced by the high metal loading (3%).

  • Stability of ruthenium catalysts supported by aerogel mixed oxides during the wet air oxidation of p-hydroxybenzoic acid in a continuous reactor

     Triki, Mohamed; Dafinov, Antonio; Llorca Pique, Jordi; Medina, Francisco
    Reaction kinetics mechanisms and catalysis
    Date of publication: 2012-12
    Journal article

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    Continuous catalytic wet air oxidation was investigated as a suitable treatment of p-hydroxybenzoic acid chosen as a phenolic compound typically found in olive mill wastewater. The reaction was conducted in a continuous reactor at 140 or 150 C and 50 bar of air using ruthenium catalysts supported by aerogel mixed oxides (Ru/CeO2–Al2O3, Ru/CeO2–TiO2). The influence of the Ru precursor and the nature of the support were studied. The results show that supported ruthenium catalysts were active to oxidize p-hydroxybenzoic acid and that the catalytic activity is very stable.

  • Hydrogen production from ethanol over Pd-Rh/CeO2 with a metallic membrane reactor

     López, Eduardo; Jimenez Divins, Nuria; Llorca Pique, Jordi
    Catalysis today
    Date of publication: 2012-10-15
    Journal article

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    The present paper reports on experimental results of an ethanol reformer equipped with a Pd-based metallic membrane toward the production of pure hydrogen, suited for PEM-fuel cell feeding. The ethanol steam reforming is conducted using a Pd–Rh/CeO2 catalyst over cordierite monoliths, which were implemented in-series into a stainless-steel membrane reactor. Inconel membranes functionalized with Pd–Ag over an adequate support were profited for hydrogen separation from the monoliths outlet. The unit was successfully tested for hydrogen production from ethanol steam reforming, achieving pure-hydrogen flowrates up to 110 mLN/min. Reaction yields of 3.1 mol hydrogen generated per mol ethanol in feed and total yields of 1.4 mol H2 permeated per mol ethanol in feed were measured, with maximum hydrogen recuperation of 70%. We discuss here the influence of the different operation parameters, as temperature, reaction (retentate) pressure, load and/or composition of the feed on the device performance. Temperatures of ca. 650 ◦C, retentate pressures of 9–11 bar and water contents in feed slightly over-stoichiometric revealed optimal for the unit operation.

  • Catalytic Performance of Solution Combustion Synthesized Alumina- and Ceria-Supported Pt and Pd Nanoparticles for the Combustion of Propane and Dimethyl Ether (DME)

     Colussi, Sara; Gayen, Arup; Llorca Pique, Jordi; de Leitenburg, Carla; Dolcetti, Giuliano; Trovarelli, Alessandro
    Industrial and engineering chemistry research (Online)
    Date of publication: 2012-01
    Journal article

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  • The study of catalysts by transmission electron microscopy techniques

     Llorca Pique, Jordi
    Date of publication: 2012-09-11
    Book chapter

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  • Dels asteroides als meteorits

     Llorca Pique, Jordi
    Date of publication: 2012-04-01
    Book chapter

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  • In situ studies of CeO 2-supported Pt, Ru, and Pt-Ru alloy catalysts for the water-gas shift reaction: Active phases and reaction intermediates

     Xu, W.; Si, Rui; Senanayake, Sanjaya D.; Llorca Pique, Jordi; Idriss, Hicham; Stacchiola, Darío J.; Hanson, Jonathan C.; Rodríguez, Jose Antonio Bertinatto
    Journal of catalysis
    Date of publication: 2012-07
    Journal article

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  • Higher activity of diesel soot oxidation over polycrystalline ceria and ceria-zirconia solid solutions from more reactive surface planes

     Aneggi, Eleonora; de Leitenburg, Carla; Llorca Pique, Jordi; Trovarelli, Alessandro
    Catalysis today
    Date of publication: 2012-12-15
    Journal article

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    High temperature treatment under air of samples of polycrystalline ceria and ceria¿zirconia is shown to induce a rearrangement of crystals, with a surface structural evolution of the oxides toward the formation of more reactive exposed planes belonging to the {1 0 0} and {1 1 0} families, associated with a decrease of the exposure of the less reactive {1 1 1} facets. This is dependent on the amount of ceria, being more evident with pure CeO2, and less important with increasing ZrO2 content. A correlation between the exposure of more reactive planes and the specific rate of carbon soot oxidation is found, in agreement with previous results obtained in monodimensional nanoshaped and polycrystalline ceria samples for CO oxidation. This suggests that Diesel soot oxidation catalysts might be designed by keeping into consideration also these effects.

  • Cobalt hydrotalcite for the steam reforming of ethanol with scarce carbon production

     Espinal, Raul; Taboada, E.; Molins, E.; Medina, Francisco; Chimentao, Ricardo J; Llorca Pique, Jordi
    RSC Advances
    Date of publication: 2012
    Journal article

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  • Cobalt hydrotalcites as catalysts for bioethanol steam reforming. The promoting effect of potassium on catalyst activity and long-term stability

     Espinal, Raul; Taboada, E.; Molins, E.; Chimentao, Ricardo J; Medina, Francisco; Llorca Pique, Jordi
    Applied catalysis B. Environmental
    Date of publication: 2012-10-30
    Journal article

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    Cobalt hydrotalcite-derived catalysts, doped with potassium, are active materials for the ethanol steam reforming reaction. Potassium addition reduces the acid sites number and strength. It acts as a promoter of the ethanol steam reforming (ESR); ethanol conversion is higher at lower temperature, as the amount of potassium at the surface of the catalyst increases. The catalysts are stable for long-term experiments (300 h) under high loads of ethanol and bioethanol (0.036 gEtOH min−1, H2O:CH3CH2OH = 4:1 molar). Moreover, they generate a low amount of carbon (0.0067 gC gcatalyst−1 h−1). The catalysts after reaction contain almost exclusively high spin Co2+ in cobalt oxide (or in (Co,Mg)O); only traces of metallic cobalt are identified by magnetometry, <0.1 wt.% Co0, suggesting that oxidized cobalt is an active species in ESR.

  • Gas-phase hydrodechlorination of trichloroethylene over Pd/NiMgAl mixed oxide catalysts

     Meshesha, B.T.; Barrabes, N.; Foettinger, Karin; Chimentao, Ricardo J; Llorca Pique, Jordi; Medina, Francisco; Rupprechter, Guenther; Sueiras, J.E.
    Applied catalysis B. Environmental
    Date of publication: 2012-05-18
    Journal article

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