Jorge Gascon

University of Valencia, Valenza, Valencia, Spain

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Publications (111)339.35 Total impact

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    ABSTRACT: Abstracts: * Porous aromatic polymers as heterogeneous catalysts.pdf (182.8KB) - Uploading Abstracts
    14 AIChE Annual Meeting; 11/2014
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    ABSTRACT: Adsorptive characterization using nitrogen at 77 K is one of the most widely used techniques to assess textural properties of porous adsorbents. Especially the pore volume, specific surface area and pore size distribution are frequently reported. Despite the fact that most popular methods to deduce these quantities, the method posed by Brunauer, Emmet and Teller (BET) [1] for the specific surface area and the method developed by Barrett, Joyner and Halenda (BJH) for pore the pore size distribution, [2] have been used for many decades, there are still inconsistencies in the exact calculation procedure of these methods and still wrong and/or statistically insignificant conclusions therefrom, as will be elucidated in detail in this contribution. Based on a thorough error analysis on the accuracy of volumetric nitrogen adsorption measurements, the influence of experimental uncertainties is analysed. This yields not only insights in the uncertainty in derived properties (pore volume, BET surface area and BJH pore size-distribution) but also generates practical recommendations to optimize accuracy of N2 adsorption measurements. Consequently, guidelines are developed to obtain representable accurate textural properties. Especially the derivation of specific surface areas requires attention, as erroneous results are easily obtained. A variety of sorbents (MOFs, zeolite, activated carbon and alumina) has been used in this work to ensure that obtained conclusions and posed guidelines hold for a wide range of commonly used porous materials. For (BJH) pore size distributions, statistically irrelevant or highly inaccurate results are frequently obtained. MIL-101, arguably the metal-organic framework (MOF) most reported on, has been characterized by a multitude of researchers and serves thus well to exemplify the current state of characterization using N2 sorption in literature. In many cases the determination of pore volume and specific surface areas has been executed wrongly and underlines a clear potential for standardized determination conditions for textural properties. In summary, to improve the meaningfulness of derived properties and to minimize statistical uncertainties, practical recommendations and guidelines are proposed for experimental operation variables and data analysis. Some of these are: * The relative uncertainty in pore volume is lowest when the Vmanifold/Vcell ratio is between 2 and 3. * A simple two-point BET method is proposed to determine a priori the upper relative pressure boundary of the BET window (close to saturation), as alternative to the method reported by Rouquerol et al. * For the lower relative pressure limit determination it is suggested to analyse Studentized residuals. Provided the model isotherm is correct, data points become eligible for possible exclusion when | resis| > 2-3. * The magnitude of the 95% confidence interval found for BJH-pore size distributions severely impedes drawing quantitative conclusions. REFERENCES [1] S. Brunauer, P.H. Emmett, E. Teller, Adsorption of gases in multimolecular layers, Journal of the American Chemical Society, 60 (1938) 309-319. [2] E.P. Barrett, L.G. Joyner, P.P. Halenda, The Determination of Pore Volume and Area Distributions in Porous Substances. I. Computations from Nitrogen Isotherms, Journal of the American Chemical Society, 73 (1951) 373-380.
    Microporous and Mesoporous Materials 11/2014; 200:199–215. · 3.37 Impact Factor
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    ABSTRACT: Composites incorporating two-dimensional nanostructures within polymeric matrices have potential as functional components for several technologies, including gas separation. Prospectively, employing metal-organic frameworks (MOFs) as versatile nanofillers would notably broaden the scope of functionalities. However, synthesizing MOFs in the form of freestanding nanosheets has proved challenging. We present a bottom-up synthesis strategy for dispersible copper 1,4-benzenedicarboxylate MOF lamellae of micrometre lateral dimensions and nanometre thickness. Incorporating MOF nanosheets into polymer matrices endows the resultant composites with outstanding CO2 separation performance from CO2/CH4 gas mixtures, together with an unusual and highly desired increase in the separation selectivity with pressure. As revealed by tomographic focused ion beam scanning electron microscopy, the unique separation behaviour stems from a superior occupation of the membrane cross-section by the MOF nanosheets as compared with isotropic crystals, which improves the efficiency of molecular discrimination and eliminates unselective permeation pathways. This approach opens the door to ultrathin MOF-polymer composites for various applications.
    Nature materials. 11/2014;
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    ABSTRACT: Functionalization of metal–organic frameworks results in higher hydrogen uptakes owing to stronger hydrogen–host interactions. However, it has not been studied whether a given functional group acts on existing adsorption sites (linker or metal) or introduces new ones. In this work, the effect of two types of functional groups on MIL-101 (Cr) is analyzed. Thermal-desorption spectroscopy reveals that the −Br ligand increases the secondary building unit’s hydrogen affinity, while the −NH2 functional group introduces new hydrogen adsorption sites. In addition, a subsequent introduction of −Br and −NH2 ligands on the linker results in the highest hydrogen-store interaction energy on the cationic nodes. The latter is attributed to a push-and-pull effect of the linkers.
    The Journal of Physical Chemistry C 07/2014; 118(34):19572-19579. · 4.84 Impact Factor
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    ABSTRACT: Several Al-based MOFs of the CAU family have been investigated for application in adsorption driven allocation of heat and cold. The special water adsorption behaviour of CAU-10-H makes it ideal for application in adsorption driven heat pumps and chillers. For increased performance, CAU-10-H crystals have been grown directly on both γ-alumina and metallic aluminium. Crystal growth on these surfaces can be controlled by the addition of acids.
    CrystEngComm 07/2014; · 3.88 Impact Factor
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    ABSTRACT: A straightforward synthetic route to chiral metal–organic frameworks is proposed that relies on an acid–base interaction between an acid linker and a chiral primary amino acid derived diamine organocatalyst. High ee values for the aldol condensation of linear ketones and aromatic aldehydes are reported with this heterogeneous catalyst. Three consecutive catalyst reuse experiments demonstrated that the majority of the activity was preserved, as was the enantioselectivity.
    ChemCatChem 07/2014; · 5.18 Impact Factor
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    ABSTRACT: Simulation of gas adsorption in flexible porous materials is still limited by the slow progress in the development of flexible force fields. Moreover, the high computational cost of such flexible force fields may be a drawback even when they are fully developed. In this work, molecular simulations of gas adsorption and diffusion of carbon dioxide and methane in NH2-MIL-53(Al) are carried out using a linear combination of two crystallographic structures with rigid force fields. Once the interactions of carbon dioxide molecules and the bridging hydroxyls groups of the framework are optimized, an excellent match is found for simulations and experimental data for the adsorption of methane and carbon dioxide, including the stepwise uptake due to the breathing effect. In addition, diffusivities of pure components are calculated. The pore expansion by the breathing effect influences the self-diffusion mechanism and much higher diffusivities are observed at relatively high adsorbate loadings. This work demonstrates that using a rigid force field combined with a minimum number of experiments, reproduces adsorption and simulates diffusion of carbon dioxide and methane in the flexible metal-organic framework NH2-MIL-53(Al).
    Physical Chemistry Chemical Physics 06/2014; · 4.20 Impact Factor
  • ChemInform 06/2014; 45(23).
  • ChemInform 05/2014; 45(20).
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    ABSTRACT: Reticular design is a highly attractive concept, but coordination chemistry around the tectonic units of metal–organic frameworks (MOFs) and additional interplay with anionic and solvent species provide for dazzling complexity that effectively rules out structure prediction. We can however study the chemistry around pre-existing clusters, and assemble novel materials correspondingly, using a priori information about the connectivity of an investigated metal cluster. Studies, often spectroscopic of nature, have in recent years solved many puzzles in MOF crystallization. The obtained knowledge opens new doors in crystal engineering, but more research on MOF coordination chemistry has to be carried out.
    ChemInform 04/2014; 45(14).
  • ChemInform 04/2014; 45(14).
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    ABSTRACT: In situ NMR and DFT modeling demonstrate that N,N-dimethylformamide (DMF) promotes the formation of metal-organic framework NH2-MIL-101(Al). In situ NMR studies show that upon dissociation of an aluminum-coordinated aqua ligand in NH2-MOF-235(Al), DMF forms a H-Cl-DMF complex during synthesis. This reaction induces a transformation from the MOF-235 topology into the MIL-101 topology. Electronic structure density functional theory (DFT) calculations show that the use of DMF instead of water as the synthesis solvent decreases the energy gap between the kinetically favored MIL-101 and thermodynamically favored MIL-53 products. DMF therefore promotes MIL-101 topology both kinetically and thermodynamically.
    Inorganic Chemistry 01/2014; 53(2):882–887. · 4.59 Impact Factor
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    ABSTRACT: Mixed matrix membranes (MMMs) composed of metal organic framework (MOF) fillers embedded in a polymeric matrix represent a promising alternative for CO2 removal from natural gas and biogas. Here, MMMs based on NH2-MIL-53(Al) MOF and polyimide are successfully synthesized with MOF loadings up to 25 wt% and different thicknesses. At 308 K and ΔP = 3 bar, the incorporation of the MOF filler enhances CO2 permeability with respect to membranes based on the neat polymer, while preserving the relatively high separation factor. The rate of solvent evaporation after membrane casting proves key for the final configuration and dispersion of the MOF in the membrane. Fast solvent removal favours the contraction of the MOF structure to its narrow pore framework configuration, resulting in enhanced separation factor and, particularly, CO2 permeability. The study reveals an excellent filler-polymer contact, with ca. 0.11% void volume fraction, for membranes based on the amino-functionalized MOF, even at high filler loadings (25 wt%). By providing precise and quantitative insight into key structural features at the nanoscale range, the approach provides feedback to the membrane casting process and therefore it represents an important advancement towards the rational design of mixed matrix membranes with enhanced structural features and separation performance.
    Advanced Functional Materials 01/2014; 24(2). · 10.44 Impact Factor
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    ABSTRACT: Graphical abstract Figure optionsDownload full-size imageDownload as PowerPoint slide
    Microporous and Mesoporous Materials 01/2014; 197:268–277. · 3.37 Impact Factor
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    ABSTRACT: Mixed matrix membranes (MMMs) composed of metal organic framework (MOF) fillers embedded in a polymeric matrix represent a promising alternative for CO2 removal from natural gas and biogas. Here, MMMs based on NH2‐MIL‐53(Al) MOF and polyimide are successfully synthesized with MOF loadings up to 25 wt% and different thicknesses. At 308 K and ΔP = 3 bar, the incorporation of the MOF filler enhances CO2 permeability with respect to membranes based on the neat polymer, while preserving the relatively high separation factor. The rate of solvent evaporation after membrane casting proves key for the final configuration and dispersion of the MOF in the membrane. Fast solvent removal favours the contraction of the MOF structure to its narrow pore framework configuration, resulting in enhanced separation factor and, particularly, CO2 permeability. The study reveals an excellent filler‐polymer contact, with ca. 0.11% void volume fraction, for membranes based on the amino‐functionalized MOF, even at high filler loadings (25 wt%). By providing precise and quantitative insight into key structural features at the nanoscale range, the approach provides feedback to the membrane casting process and therefore it represents an important advancement towards the rational design of mixed matrix membranes with enhanced structural features and separation performance.
    Advanced Functional Materials 01/2014; 24(2). · 10.44 Impact Factor
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    ABSTRACT: Mesoporous H‐ZSM‐5 (mesoH‐ZSM‐5) was used as a carrier for a series of bifunctional Co‐based catalysts for Fischer–Tropsch synthesis with ZrO2 and/or Ru added as promoters. The reducibility of the catalysts was studied in detail by using temperature‐programmed reduction and X‐ray absorption spectroscopy. A comparison of the catalytic performance of Co/mesoH‐ZSM‐5 and Co/SiO2 (a conventional catalyst), after 140 h on stream, reveals that the former is two times more active and three times more selective to the C5–C11 fraction with a large content of unsaturated hydrocarbons, which is next to α‐olefins. The acid‐catalyzed conversion of n‐hexane and 1‐hexene, as model reactions, demonstrates that the improvement in the selectivity toward gasoline range hydrocarbons is due to the acid‐catalyzed reactions of the Fischer–Tropsch α‐olefins over the acidic zeolite. The formation of methane over the zeolite‐supported Co catalysts originates from direct CO hydrogenation and hydrocarbon hydrogenolysis on coordinatively unsaturated Co sites, which are stabilized as a consequence of a strong metal–zeolite interaction. Although the addition of either ZrO2 or Ru increases the catalyst reducibility considerably, it does not affect the product selectivity significantly.
    ChemCatChem 01/2014; 6(1). · 5.18 Impact Factor
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    ABSTRACT: High-silica (gel Si/Al = 100) SSZ-13 membranes were prepared by hydrothermal secondary growth on the surface of [small alpha]-alumina hollow fiber supports. The membranes were evaluated for their performance in the separation of CO2 from equimolar mixtures with CH4 or N2. The maximum CO2-CH4 and CO2-N2 separation selectivities were found to be 42 and 12 respectively, with a high CO2 permeance of 3.0 [times] 10-7 mol m2 s-1 Pa-1 at 293 K and total feed pressure of 0.6 MPa. At the low aluminum content, the prepared membranes contain a very low number of defects, as follows from their H2/SF6 ideal selectivity of over 500 in the 293-473 K temperature range. Due to their hydrophobicity, water in the feed mixture has only a small influence on the permeance at temperatures above 353 K. Water improves the CO2-N2 and CO2-CH4 selectivity, which is attributed to preferential blocking of the hydrophilic, non-zeolitic defect pores. The hydrothermal stability of the high-silica SSZ-13 membrane was evaluated by a lon
    Journal of Materials Chemistry A: Materials for Energy and Sustainability 01/2014; 2(32):13083-13092.
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    ABSTRACT: a b s t r a c t Cerium-doped cryptomelane stabilizes polyhedron Au nano-particles smaller than 3 nm. The obtained Au/Ce/cryptomelane catalyst is highly active for CO oxidation. Cationic, neutral, and anionic gold species were found on Ce/cryptomelane. The modification of cryptomelane by the addition of cerium is twofold: (i) cerium is incorporated in the tunnels of cryptomelane, increasing the number of defects which func-tion as nucleation sites for gold and (ii) ceria nano-particles at the surface induce charge transfer between gold and cryptomelane. TOF for Au/Ce–K-OMS-2 is about twice that of Au/CeO 2 prepared by the same procedure.
    Journal of Catalysis 01/2014; 309:58-65. · 5.79 Impact Factor
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    ABSTRACT: In this perspective, we highlight the main opportunities of metal organic frameworks (MOFs) as heterogeneous catalysts. Along with our personal view on the most promising catalytic applications, the most important issues that still need to be addressed before commercial implementation of MOF catalysis are discussed.
    ACS Catalysis 12/2013; 4(2):361–378. · 5.27 Impact Factor
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    ABSTRACT: Design and operation of a "six-flow fixed-bed microreactor" setup for Fischer-Tropsch synthesis (FTS) is described. The unit consists of feed and mixing, flow division, reaction, separation, and analysis sections. The reactor system is made of five heating blocks with individual temperature controllers, assuring an identical isothermal zone of at least 10 cm along six fixed-bed microreactor inserts (4 mm inner diameter). Such a lab-scale setup allows running six experiments in parallel, under equal feed composition, reaction temperature, and conditions of separation and analysis equipment. It permits separate collection of wax and liquid samples (from each flow line), allowing operation with high productivities of C5+ hydrocarbons. The latter is crucial for a complete understanding of FTS product compositions and will represent an advantage over high-throughput setups with more than ten flows where such instrumental considerations lead to elevated equipment volume, cost, and operation complexity. The identical performance (of the six flows) under similar reaction conditions was assured by testing a same catalyst batch, loaded in all microreactors.
    The Review of scientific instruments 12/2013; 84(12):124101. · 1.52 Impact Factor

Publication Stats

414 Citations
339.35 Total Impact Points

Institutions

  • 2014
    • University of Valencia
      Valenza, Valencia, Spain
  • 2008–2014
    • Delft University Of Technology
      • • Department of Chemical Engineering
      • • Catalysis Engineering Group
      Delft, South Holland, Netherlands
  • 2013
    • Cambridge Eco
      Cambridge, England, United Kingdom
  • 2009–2012
    • Free University of Brussels
      • Department of Chemical Engineering (CHIS)
      Brussels, BRU, Belgium
  • 2011
    • Brookhaven National Laboratory
      New York City, New York, United States
  • 2004–2011
    • University of Zaragoza
      • Department of Chemical Engineering and Environmental Technology
      Zaragoza, Aragon, Spain